Learn C++ first and you can then do ANYTHING!

Develop games, CHECK!

Develop rockets that land themselves, CHECK! (SpaceX rockets use C++ to land themselves!).

Help astronomers and astrophysicists develop cosmological simulations, CHECK!

Backend corporate applications? CHECK!

As for C#, it's a really nice language but... it's trapped in MS-Windows land, and mainly used for corporate user interfaces (like forms, etc...).

There's some gaming developed with C#, but nothing as powerful and as industry-wide standard as C++.

C++ is the language to rule them all.

After that you can learn Python, which will be a breeze and walk in the park if you know C++. (You'll probably be able to learn most of the basics of Python in just one weekend, if you already know C++!).

So ya, if you want to be a serious programmer, then I would live and breathe C++ for the next few months.