facebook
favorite button
super instructor icon
Vertrauter Lehrer
Dieser Lehrer hat eine schnelle Reaktionszeit, was eine hohe Servicequalität für seine Schüler beweist.
member since icon
Seit Dezember 2025
Lehrer seit Dezember 2025
KS3 Maths & English
course price icon
Von 38.32 Fr /Std
arrow icon
This KS3 Maths & English class is designed to help students build strong foundations, boost confidence, and make consistent progress in both subjects.

In Maths, students will develop key skills in number, fractions, percentages, algebra, geometry, and problem-solving. Lessons focus on understanding methods, improving accuracy, and applying skills confidently in exams and real-world contexts.

In English, students will strengthen reading comprehension, spelling, punctuation and grammar, vocabulary, and writing skills. Students will work on both creative and functional writing, while also developing confidence in speaking and expressing ideas clearly.

Sessions are tailored to each student’s level, with clear explanations, structured practice, and ongoing feedback. This class is ideal for students who need extra support, want to close learning gaps, or are aiming to improve their overall performance at Key Stage 3.
Zusätzliche Informationen
Online classes ensure stable internet connection
Ort
location type icon
Online aus Vereinigtes Königreich
Über mich
Hello!

My name is Ishnoor, and I am a BSc (Hons) Public Health student at the University of Manchester. As a recipient of the Sheikha Fatima Award and the Crest Gold Award, I am deeply committed to academic excellence and helping others reach their full potential. My journey in education has been global, including earning a 100% scholarship to the University of Cambridge’s Medicine Summer School.

I believe that education has the power to transform lives and should transcend the traditional classroom. I have extensive experience in mentorship and instruction, having founded an online initiative where I mentored over 400 children in English, public speaking, and debating. Currently, I serve as an Academic Representative at my university and work as a GCSE tutor, where I focus on building my students' confidence and helping them overcome academic challenges.

My tutoring approach is rooted in:
* Empowerment: Helping students find their unique voice and academic strengths.
* Holistic Growth: Encouraging critical thinking, authentic communication, and leadership.
* Proven Experience: Years of experience as a debate coach and moderator, fostering cultures of excellence and teamwork.

Whether your goal is to master GCSE/ IB subjects or improve public speaking and essay writing or work on your university application, I am dedicated to providing a supportive and enriching environment to help you succeed.
Bildung
University of Manchester BSc Public Health (Year 1)
IB Diploma
GCSE
Erfahrung / Qualifikationen
Tutored over 400+ students
Alter
Kinder (7-12 Jahre alt)
Jugendliche (13-17 Jahre alt)
Unterrichtsniveau
Anfänger
Mittel
Fortgeschritten
Dauer
30 Minuten
45 Minuten
60 Minuten
90 Minuten
Unterrichtet in
Englisch
Hindi
Panjabi
Fachkenntnisse
Verfügbarkeit einer typischen Woche
(GMT -05:00)
New York
at teacher icon
Online via Webcam
Mon
Tue
Wed
Thu
Fri
Sat
Sun
00-04
04-08
08-12
12-16
16-20
20-24
This class is designed to help students become confident, articulate speakers who can express ideas clearly and persuasively.

Students develop key skills in public speaking, debating, and speech writing, learning how to structure arguments, think critically, and communicate with confidence. Lessons focus on building strong content, using effective language, and delivering speeches clearly and convincingly.

Through guided practice and interactive activities, students learn how to present ideas, respond to questions, and engage an audience. Debating activities help students develop logical reasoning, teamwork, and the ability to consider different viewpoints. Speech writing sessions focus on planning, structure, persuasive techniques, and refining written work for oral delivery.

The class provides a supportive environment where students build confidence, improve clarity of expression, and develop essential communication skills that benefit academic performance and everyday life.

This class is designed for students who want to develop high-level essay writing skills for competitions, school assessments, and academic success.

Drawing on extensive experience in essay competitions and having earned a fully funded (100%) scholarship to the University of Cambridge Summer School through competitive writing, lessons focus on what truly makes an essay stand out. Students learn how to develop original ideas, build clear and persuasive arguments, structure essays effectively, and write with precision and confidence.

Sessions cover planning and research, crafting strong introductions and conclusions, developing coherent paragraphs, and refining academic tone and style. Students also receive personalised feedback and guidance on improving clarity, depth of analysis, and originality—key skills required for top marks and competitive success.

This class is ideal for students preparing for essay competitions, GCSE/IB extended writing, personal statements, or enrichment beyond the curriculum.
Mehr lesen
This GCSE class provides comprehensive support across a range of subjects, helping students build strong understanding, confidence, and exam readiness.

Subjects covered include GCSE Maths (including Further Maths), Biology, Chemistry, English, Psychology, Art & Design, and Design & Technology.

Lessons are tailored to each student’s needs and focus on clear explanations, structured practice, and effective exam technique. In Maths and Further Maths, students develop strong problem-solving skills and confidence with higher-level content. In the sciences, lessons focus on understanding key concepts, applying knowledge accurately, and answering exam questions effectively. English tuition supports reading, writing, analysis, and communication skills across both Language and Literature.

For Psychology, students are guided through key theories, research methods, and exam-style responses. Art & Design and Design & Technology tuition supports both creative development and coursework, including planning, experimentation, annotation, and exam preparation.

Sessions are structured, supportive, and results-focused, with regular feedback and targeted practice to help students improve performance and achieve their full potential at GCSE level.
Mehr lesen
Show more
arrow icon
Ähnliche Kursen
arrow icon previousarrow icon next
verified badge
Bonjour,

Each course is prepared for your purposes.
I am on my way to school

I need the phonology/pronunciation/oral conversation course.
I support many adults in their transition. They need to converse and write in English for professional purposes (accent reduction, grammar, oral fluency, etc.) or as part of a revision course.

I am a language teacher.

In English:

Each course is prepared according to your personal needs.

I can intervene at the following levels:

- School:

College-High School => Correction/Improvement of grammar + other language activities such as oral/written comprehension or continuous speaking/interaction

(Linguistics / Phonology / Pronunciation)

- I accompany and have accompanied many adults who really had to speak/write English successfully as part of their professional activities (fluency, accent reduction, grammar ...) or as part of resuming their studies.

I am a trained linguist. Lessons cannot be improvised. I offer you the fruits of my expertise.
verified badge
Fully certified TEFL/TESOL

*All classes are one-on-one and tailored to the individual student's needs and requirements. The ultimate goal is that the student thinks in the language not just translates.
*All key aspects of the language will be addressed including cultural aspects/linguistic differences.
* Whether a quick learner or not; it will be fun and comprehensible. There is a goal to achieve and it will be done.
* Whether learning a language to improve your career, for travel or even romantic reasons, help is at hand - just reach out.

Some Reviews:
Chevaan:
Catherina is without a doubt THE best tutor we know. She is exceptionally committed and is always looking to inspire her students. She has consistently gone above and beyond the call of duty to help our son with his German. She provides excellent study material, engaging homework and follows up to ensure that her students have really grasped the subject matter.

Brian:
Catharina has been teaching our 11 year old daughter for the past few months and we are very impressed with her excellent progress in this short space of time.
Catharina has developed a very good rapport with our daughter and is patient and knowledgeable. Our daughter always looks forward to her next lesson and even hands in her homework on time! We would highly recommend Catharina to anyone who would like to learn a new language.

Afeisha:
Very professional, friendly and informative. I feel like Catharina will help me to reach where I need to. She doesn't just teach from the book, she teaches in a way that will allow you to blend in with ease. I am excited to learn more from her.

Egle:
Great tutor! Catharina adapts lessons to ones needs, gives very clear explanations and most importantly works on the pronunciation of the language. With every lesson she provides lesson material.
verified badge
Master English Online with TEFL/TESOL-Certified Tutor: All Skills, Any Level

Elevate your speaking, writing, reading, and listening with customized online English from a TEFL/TESOL expert. I bring global experience teaching conversational English to non-natives, plus targeted IELTS support. Every class includes grammar, listening, and reading—structured just for you. Contact me today!

Together, we create an inviting, idea-exchanging atmosphere that deepens our student-teacher partnership.

Expect These Benefits:

Starting proficiency evaluations

Personalized lessons fitting your learning approach

Bespoke study resources

Dynamic conversation sessions

Thorough lesson recaps

Feedback on your writing

Reliable inter-lesson check-ins, all remotely

Individualized one-on-one guidance
verified badge
The objective is that: the learner masters the English language (🎧listening-comprehension,🎤 conversation, 📚 reading, grammar-pronunciation, writing...). It helps him to have language skills like native speakers. 🥇

At the same time, the learner will be 🚴‍♀️dynamic and well supervised by professional tutors who listen.
The atmosphere is distinguished: 🔥learning, interaction, no routine, no stress.

The learning tools used; videos, audios, texts, articles, images, games, stories...

We are happy to help both adults and pupils/students. If you want to learn the English language (reading, grammar, oral conversation, written production,...) or you have homework to do, or competitions/tests to take, 🏆 contact us :)
verified badge
High School Math can be confusing for students. Often there is not enough time in school to repeat the content and practice enough, for the students to gain confidence and a routine in solving mathematical problems. With my help and guidance, any confusion will be cleared and we will practice problem solving until you are confident and understand the material.

The lessons will be tailored to your needs and their structure depends highly on you: usually it is a mixture of repeating the content, solving exercises together, summarising important concepts and talking about exercises you tried yourself at home. The topics, content, pace and methods of learning will be adjusted to your needs, ensuring that you get the most out of my lessons. Besides the lessons, you will get "homework" to work on to strengthen your skills and independent working.

Topics include, but are not limited to:
-Linear Algebra
-Calculus
-Trigonometry
-Geometry
-Set Theory
-Analysis

If you have another topic in mind that you really need help with, just send me a message!

Whether you need someone that explains the concepts to you or just someone to practice exercises with - I am sure I can help you. You have an exam soon and want to review the main topics? No problem! You have a very specific problem, question or topic that you need help with? I'm here to answer any questions! You need help with preparing for your A-levels/High School diploma? Don't fret, I will guide and prepare you!

The most important part of my lessons is, however, to ensure a safe and comfortable environment - I have no issue with explaining the same concept over and over again until I am convinced that you have understood it. It is important to me that you feel comfortable in asking any questions - I want to show you, that Math is more than a subject and that it can be fun!
verified badge
Struggling with school math or aiming for exam excellence? In this class, I make complex topics simple, clear, and even enjoyable. From middle school to university level math, I adapt to every student's level and mindset. Whether it's building strong foundations or mastering advanced concepts, you or your child will walk away feeling confident, capable, and ready to shine.

✨ Personalised approach
📚 Clear explanations + real understanding
🏆 Proven results in IB, OMPT, VWO & more

Let’s turn “I don’t get it” into “I’ve got this!”
Book the first session and see the difference.
verified badge
Bachelor's student in economics and management offers private lessons in German, French and English.
I obtained my bachelor's degree with a specialization in mathematics and physics and I have sufficient knowledge in mathematics, physics, chemistry, German, English and French.
In my teaching, I adapt to the learning conditions and the student's life in order to strengthen their self-confidence and ensure that they understand the lessons and progress.
My goal is to create an effective learning environment. I rely on the student's course, which I supplement if necessary with additional information.
verified badge
اسمي إيمان، أنا معالج لغة وكلام معتمد في كلية الطب، جامعة عين شمس، القاهرة، مصر.
العمل في مستشفى دمرداش ومستشفى عين شمس التخصصي كمعالج لغة وكلام.
كما أعمل كأخصائي تخاطب في عيادة طبيب تخاطب أ.د\محمد بركة, أستاذ أمراض التخاطب بكلية الطب جامعة عين شمس.
أتممت دراسة البكالوريوس والماجستير في «تربية الطفل» في كلية التربية للطفولة المبكرة، جامعة القاهرة، مصر.

وأدرس حاليا الدكتوراه في اضطرابات النطق والصوت في كلية التربية للطفولة المبكرة، جامعة القاهرة، مصر.

أقدم جلسات حضور مباشرة وجلسات عبر الإنترنت عبر التكبير وكاميرا في:

تعلم تحدث اللغة العربية (الفصحي والعامية) لغير الناطقين بها.
من خلال سرد مواقف حياتية ومشاركة الاهتمامات (والألعاب والقصص بالنسبة لحالات الأطفال) بطريقة ممتعة وفكاهية بعيدا عن الجمود والتقليدية.

Another example is:
1- غير الناطقين للغة العربية من جميع الأعمار.
2- العرب من الأطفال تحدث اللغة العربية.
verified badge
I teach German courses on the largest online sites and other platforms for all Goethe levels from A.1 to C.1 as well as special courses for beginners and advanced students as well as senior high school students in Egypt in the largest institutes as I am an expert in the German language in state secondary schools and a certified teacher in the largest platforms: I have a Master's degree in German Literature from the University of Vienna, Austria
I also speak Arabic, my native language
I am also fluent in English
verified badge
English course for beginners improving the four skills listening, reading, writing and speaking. learning how to understand the street language and how to speak like them and gain the American accent easily.
An English language course from scratch with the development of the four skills: listening, speaking, writing, reading, training in the American dialect, and learning about slang or street language in an easy way.
verified badge
I am a Translator-Interpreter and have worked in marketing for an American Petroleum Company for 25 years.
My knowledge of languages was very crucial. After my husband's premature death I did replacements but after a while I started giving private language lessons. I spoke French until I was six.
verified badge
A graduate in Germanic languages, I have been a secondary school English/German teacher since 2021 and a private tutor since 2017. I also coordinate language camps and ONE centers and offer private English lessons. Whether you need academic support, want to meet professional challenges, are starting English from scratch, are looking to improve your skills, focus on grammar, speaking, or have other goals, I am available.

I offer lessons, but my main goal is to empower you to learn English, and languages in general, independently. I don't aim for the level of excellence you think you're currently in, but rather the level of excellence you allow yourself to achieve. My ultimate goal: that you no longer need me.

Each lesson is prepared in advance. I never arrive empty-handed.
verified badge
I offer academic support in mathematics, French and German for primary and secondary school students (first year of high school).
I will help you with your homework, with tailored explanations, test preparation, etc.
I can also give you extra exercises to train with if needed!
verified badge
What I offer:
Social Studies & Science taught in English
Clear explanations adapted to the student's level
Support with school curriculum & exams
Interactive lessons using visuals, activities & discussions
Suitable for Primary & Middle School students
🔹Why choose me? ✔ Patient & supportive teaching style
✔ Focus on understanding, not memorization
✔ Boost academic performance & confidence
📌 Book a lesson today and make learning easier and more enjoyable!
verified badge
Do you feel insecure when speaking English? Do you need someone to practice with regularly to improve your pronunciation, confidence, and overall speaking skills? Then let's work on it together. I have a degree in English Literature and Culture as well as a Cambridge Certificate.

With me you will:

- specifically improve your pronunciation

- gain more confidence when speaking

- expand your vocabulary

- and solidify your grammar step by step

I'd also be happy to support you with your writing: We can work together on your texts and significantly improve your written expression.

And if you're about to graduate from high school, I offer you a compact, effective crash course so you can get off to a great start, fully prepared.
message icon
Ishnoor kontaktieren
repeat students icon
Der richtige Lehrer Garantie
Ähnliche Kursen
arrow icon previousarrow icon next
verified badge
Bonjour,

Each course is prepared for your purposes.
I am on my way to school

I need the phonology/pronunciation/oral conversation course.
I support many adults in their transition. They need to converse and write in English for professional purposes (accent reduction, grammar, oral fluency, etc.) or as part of a revision course.

I am a language teacher.

In English:

Each course is prepared according to your personal needs.

I can intervene at the following levels:

- School:

College-High School => Correction/Improvement of grammar + other language activities such as oral/written comprehension or continuous speaking/interaction

(Linguistics / Phonology / Pronunciation)

- I accompany and have accompanied many adults who really had to speak/write English successfully as part of their professional activities (fluency, accent reduction, grammar ...) or as part of resuming their studies.

I am a trained linguist. Lessons cannot be improvised. I offer you the fruits of my expertise.
verified badge
Fully certified TEFL/TESOL

*All classes are one-on-one and tailored to the individual student's needs and requirements. The ultimate goal is that the student thinks in the language not just translates.
*All key aspects of the language will be addressed including cultural aspects/linguistic differences.
* Whether a quick learner or not; it will be fun and comprehensible. There is a goal to achieve and it will be done.
* Whether learning a language to improve your career, for travel or even romantic reasons, help is at hand - just reach out.

Some Reviews:
Chevaan:
Catherina is without a doubt THE best tutor we know. She is exceptionally committed and is always looking to inspire her students. She has consistently gone above and beyond the call of duty to help our son with his German. She provides excellent study material, engaging homework and follows up to ensure that her students have really grasped the subject matter.

Brian:
Catharina has been teaching our 11 year old daughter for the past few months and we are very impressed with her excellent progress in this short space of time.
Catharina has developed a very good rapport with our daughter and is patient and knowledgeable. Our daughter always looks forward to her next lesson and even hands in her homework on time! We would highly recommend Catharina to anyone who would like to learn a new language.

Afeisha:
Very professional, friendly and informative. I feel like Catharina will help me to reach where I need to. She doesn't just teach from the book, she teaches in a way that will allow you to blend in with ease. I am excited to learn more from her.

Egle:
Great tutor! Catharina adapts lessons to ones needs, gives very clear explanations and most importantly works on the pronunciation of the language. With every lesson she provides lesson material.
verified badge
Master English Online with TEFL/TESOL-Certified Tutor: All Skills, Any Level

Elevate your speaking, writing, reading, and listening with customized online English from a TEFL/TESOL expert. I bring global experience teaching conversational English to non-natives, plus targeted IELTS support. Every class includes grammar, listening, and reading—structured just for you. Contact me today!

Together, we create an inviting, idea-exchanging atmosphere that deepens our student-teacher partnership.

Expect These Benefits:

Starting proficiency evaluations

Personalized lessons fitting your learning approach

Bespoke study resources

Dynamic conversation sessions

Thorough lesson recaps

Feedback on your writing

Reliable inter-lesson check-ins, all remotely

Individualized one-on-one guidance
verified badge
The objective is that: the learner masters the English language (🎧listening-comprehension,🎤 conversation, 📚 reading, grammar-pronunciation, writing...). It helps him to have language skills like native speakers. 🥇

At the same time, the learner will be 🚴‍♀️dynamic and well supervised by professional tutors who listen.
The atmosphere is distinguished: 🔥learning, interaction, no routine, no stress.

The learning tools used; videos, audios, texts, articles, images, games, stories...

We are happy to help both adults and pupils/students. If you want to learn the English language (reading, grammar, oral conversation, written production,...) or you have homework to do, or competitions/tests to take, 🏆 contact us :)
verified badge
High School Math can be confusing for students. Often there is not enough time in school to repeat the content and practice enough, for the students to gain confidence and a routine in solving mathematical problems. With my help and guidance, any confusion will be cleared and we will practice problem solving until you are confident and understand the material.

The lessons will be tailored to your needs and their structure depends highly on you: usually it is a mixture of repeating the content, solving exercises together, summarising important concepts and talking about exercises you tried yourself at home. The topics, content, pace and methods of learning will be adjusted to your needs, ensuring that you get the most out of my lessons. Besides the lessons, you will get "homework" to work on to strengthen your skills and independent working.

Topics include, but are not limited to:
-Linear Algebra
-Calculus
-Trigonometry
-Geometry
-Set Theory
-Analysis

If you have another topic in mind that you really need help with, just send me a message!

Whether you need someone that explains the concepts to you or just someone to practice exercises with - I am sure I can help you. You have an exam soon and want to review the main topics? No problem! You have a very specific problem, question or topic that you need help with? I'm here to answer any questions! You need help with preparing for your A-levels/High School diploma? Don't fret, I will guide and prepare you!

The most important part of my lessons is, however, to ensure a safe and comfortable environment - I have no issue with explaining the same concept over and over again until I am convinced that you have understood it. It is important to me that you feel comfortable in asking any questions - I want to show you, that Math is more than a subject and that it can be fun!
verified badge
Struggling with school math or aiming for exam excellence? In this class, I make complex topics simple, clear, and even enjoyable. From middle school to university level math, I adapt to every student's level and mindset. Whether it's building strong foundations or mastering advanced concepts, you or your child will walk away feeling confident, capable, and ready to shine.

✨ Personalised approach
📚 Clear explanations + real understanding
🏆 Proven results in IB, OMPT, VWO & more

Let’s turn “I don’t get it” into “I’ve got this!”
Book the first session and see the difference.
verified badge
Bachelor's student in economics and management offers private lessons in German, French and English.
I obtained my bachelor's degree with a specialization in mathematics and physics and I have sufficient knowledge in mathematics, physics, chemistry, German, English and French.
In my teaching, I adapt to the learning conditions and the student's life in order to strengthen their self-confidence and ensure that they understand the lessons and progress.
My goal is to create an effective learning environment. I rely on the student's course, which I supplement if necessary with additional information.
verified badge
اسمي إيمان، أنا معالج لغة وكلام معتمد في كلية الطب، جامعة عين شمس، القاهرة، مصر.
العمل في مستشفى دمرداش ومستشفى عين شمس التخصصي كمعالج لغة وكلام.
كما أعمل كأخصائي تخاطب في عيادة طبيب تخاطب أ.د\محمد بركة, أستاذ أمراض التخاطب بكلية الطب جامعة عين شمس.
أتممت دراسة البكالوريوس والماجستير في «تربية الطفل» في كلية التربية للطفولة المبكرة، جامعة القاهرة، مصر.

وأدرس حاليا الدكتوراه في اضطرابات النطق والصوت في كلية التربية للطفولة المبكرة، جامعة القاهرة، مصر.

أقدم جلسات حضور مباشرة وجلسات عبر الإنترنت عبر التكبير وكاميرا في:

تعلم تحدث اللغة العربية (الفصحي والعامية) لغير الناطقين بها.
من خلال سرد مواقف حياتية ومشاركة الاهتمامات (والألعاب والقصص بالنسبة لحالات الأطفال) بطريقة ممتعة وفكاهية بعيدا عن الجمود والتقليدية.

Another example is:
1- غير الناطقين للغة العربية من جميع الأعمار.
2- العرب من الأطفال تحدث اللغة العربية.
verified badge
I teach German courses on the largest online sites and other platforms for all Goethe levels from A.1 to C.1 as well as special courses for beginners and advanced students as well as senior high school students in Egypt in the largest institutes as I am an expert in the German language in state secondary schools and a certified teacher in the largest platforms: I have a Master's degree in German Literature from the University of Vienna, Austria
I also speak Arabic, my native language
I am also fluent in English
verified badge
English course for beginners improving the four skills listening, reading, writing and speaking. learning how to understand the street language and how to speak like them and gain the American accent easily.
An English language course from scratch with the development of the four skills: listening, speaking, writing, reading, training in the American dialect, and learning about slang or street language in an easy way.
verified badge
I am a Translator-Interpreter and have worked in marketing for an American Petroleum Company for 25 years.
My knowledge of languages was very crucial. After my husband's premature death I did replacements but after a while I started giving private language lessons. I spoke French until I was six.
verified badge
A graduate in Germanic languages, I have been a secondary school English/German teacher since 2021 and a private tutor since 2017. I also coordinate language camps and ONE centers and offer private English lessons. Whether you need academic support, want to meet professional challenges, are starting English from scratch, are looking to improve your skills, focus on grammar, speaking, or have other goals, I am available.

I offer lessons, but my main goal is to empower you to learn English, and languages in general, independently. I don't aim for the level of excellence you think you're currently in, but rather the level of excellence you allow yourself to achieve. My ultimate goal: that you no longer need me.

Each lesson is prepared in advance. I never arrive empty-handed.
verified badge
I offer academic support in mathematics, French and German for primary and secondary school students (first year of high school).
I will help you with your homework, with tailored explanations, test preparation, etc.
I can also give you extra exercises to train with if needed!
verified badge
What I offer:
Social Studies & Science taught in English
Clear explanations adapted to the student's level
Support with school curriculum & exams
Interactive lessons using visuals, activities & discussions
Suitable for Primary & Middle School students
🔹Why choose me? ✔ Patient & supportive teaching style
✔ Focus on understanding, not memorization
✔ Boost academic performance & confidence
📌 Book a lesson today and make learning easier and more enjoyable!
verified badge
Do you feel insecure when speaking English? Do you need someone to practice with regularly to improve your pronunciation, confidence, and overall speaking skills? Then let's work on it together. I have a degree in English Literature and Culture as well as a Cambridge Certificate.

With me you will:

- specifically improve your pronunciation

- gain more confidence when speaking

- expand your vocabulary

- and solidify your grammar step by step

I'd also be happy to support you with your writing: We can work together on your texts and significantly improve your written expression.

And if you're about to graduate from high school, I offer you a compact, effective crash course so you can get off to a great start, fully prepared.
Der richtige Lehrer Garantie
favorite button
message icon
Ishnoor kontaktieren