How can I make my own android app. Should I edit tinker app code or what (I don’t want to do that)? I saw two app on github too namely Fontify and sparkCore. What should I do with them. Sorry I am too new for making android apps but have made many small apps. Is there any library that I can use?
That is a REALLY broad question, and one that cannot be answered easily. It all depends on what you need.
Anything you like. They're open source so everybody can play with it. Customise it to your needs, and make it do whatever you like it to do.