GRE

Its a good thought that you have decided to pursue your Master's abroad. You have lot of things to concentrate on apart from GRE and TOEFL. Because the universities consider your overall profile and give the admit. You have to write GRE exam when you come to the 3rd year of Engineering so that you can fly immediately as soon as you finish your Bachelor's degree. GRE is for 340 marks and its totally online based test. You'll have only Maths and English in the exam. You also need to write two essays before you proceed to the main section, its called Analytical Writing Assessment (AWA). Scores above 310 is considered to be decent provided if you have a strong academic background. Try to score 75%+ in your Bachelor's, if possible present few national or international papers. You can also improve your profile by doing internships and projects. If you are planning for USA then take TOEFL instead of IELTS as some universities in US doesn't accept IELTS score. TOEFL is for 120 marks and it purely judges your ability to Read,Listen,Speak and Write in English. Even it is an online based test.
Overall, If you have 75%+ in Bachelor's with few paper publications, research works, internships or projects, 315+ in GRE and 100+ in TOEFL. Definitely you will get into top universities in USA.
Do remember the competition is at its peak for the Masters program in US
All the best !!!

Yes learning german is helpful as you need to interact outside the course too. Since you hvnt mentioned the course you are interested in, here is the list of requirements.The eligibility criteria may differ from university to university. So please refer to the University website for the eligibility criteria for the course that interests you.
1. Academics
Certification of Undergraduate study (Bachelor degree) in similar field
2. Language Requirement
If the course is completely in German, then proof of proficiency in German Language
German as a Foreign Language Test (TestDaF)
German Language Test for the Admission of Foreign study applicants (DSH)
If the course is in English, then proof of proficiency in English TOEFL (550 and higher (PBT), 213 and higher (CBT), 79 and higher (IBT) ) or IELTS 6.0
For bilingual courses, appropriate proof may be required
3. Entrance qualification
For engineering courses, some universities may demand GRE
For Business management courses, some universities may demand GMAT
Some universities require the student to take entrance test either online or upon arrival at the campus (in the later case conditional admission is provided)
4. Work Experience
Improved chances of admission if relevant work experience in the field of further study
5. Project Work / Thesis
Demonstration of technical ability through project execution
6. Extracurricular activities
Paper presentation, participation in Technical symposium, conference etc will be highly appreciated.