Not sure if there's any open source in Github but you could check it out in there if you have the time. I believe there would be many open-source project there you could contribute.
To make an Android Application? Correct me if I am wrong but mostly you'll need to learn programming languages like Java when you use Android SDK. You could use programming languages like C in Native Dev kits.

By the way, it isn't just the languages you should need to learn. You would often hear/read OOP , functional programming, procedural, etc. Those are some paradigms of programming and you'll need to learn how do they differ as well because some languages like Java which is an OOP language differ on how you write codes. Class-based? Functional-based? It depends.

Otherwise, just hire a developer but from how you write, it seems like you have some knowledge about forking projects mostly by codings.