Languages

Hi Reyansh,
If you are applying for an undergraduate course, then German language is an absolute mandate. In addition, you must complete 13 years education that is one more year of education after class 12th. For Masters, you have to complete your Bachelor's degee. Specify what you want to study for better guidance.

Yes, you have to give an entrance test for admission in masters in English and should score minimum 60% in your graduation.

You should opt for teaching subject if you want to teach in English.

Yes in aiims and other du colleges

Just keep practicing it. Try to have conversation with others in English only. Read newspaper and watch English movies, not dubbed.

You can pursue 2 degrees simultaneously. But, both cannot be done from the same university and in regular mode.