I never understood how GitHub worked. I guess I'll have to look into it at some point, but eh. There's just so much things I don't understand and don't know if I'll ever use them. For now I'll stick with my internal storage, and making extra-sure I don't delete them again.
I don't think it's a good idea in the long run to keep your assets and codebase on your internal storage. Data corruption is pretty common.
There's good tutorials on YouTube about using GitHub. They're mostly 20 minutes long but it will save you a lifetime of pain.
If you find the command line stuff in GitHub difficult to use, then you can use GitHub Desktop instead. It's the GUI version of GitHub.