What can I do by learning java and c programming?

Answer 1

All language are multi-purposed.

Whatever you have in your mind, there is corresponding tutorial.

Java

Tutorial for coding a web server with Java

https://youtu.be/vtPkZShrvXQ

Tutorial for Android mobile app development with Java

https://www.youtube.com/playlist?list=PL_c9BZzLwBRJLm0QETVj_XcN4jRsV4LkR

C

Tutorial for coding a web server with C

https://youtu.be/Q1bHO4VbUck

Tutorial for Android mobile app development with C

https://youtu.be/YzxZAk3yttM

Answer 2

You have asked for Java earlier. Why don't you check answer for your prior question?