You just need to understand assembly. Maybe there are books that can help, I'm not aware of any, but to get started I'd recommend taking a binary of any open source software (preferably a non-optimised build, or just your own hello world with some loops etc), run it in a debugger, and step through each assembly instruction at a time and figure out what it's doing, with the corresponding source code. Eventually you may be able to do this without needing the source code, which is the goal. I think this is about the same effort as learning a new language (spoken, not programming), i.e. it'll take months of being immersed in it to get good at it.
On the other hand, maybe your binary can be decompiled to source code (e.g. CFR can decompile java classes, I've used that a bit but haven't checked if that's useful for Android apps).