Answer 1

Please use the search bar.

https://www.sololearn.com/discuss/1292168/?ref=app
https://www.sololearn.com/discuss/1303826/?ref=app
https://www.sololearn.com/discuss/1811321/?ref=app
https://www.sololearn.com/discuss/1900091/?ref=app
https://www.sololearn.com/discuss/1897653/?ref=app
https://www.sololearn.com/discuss/1373027/?ref=app

Answer 2

It depends on your goal of learning programming. If you want to be an Android programmer you can learn Java.
If you want to use programming for scientific goals you can learn MATLAB or Python.
If you want to program for Windows you can learn C#, Java, C++, and...

Answer 3

Woah there. You've completed the SoloLearn C beginners tutorial. You're not even close to finished. Don't try and learn as many languages as possible, instead you should continue to improve you C. Do some projects, read the K&R C book, etc.