Reverse engineering is not onerously difficult if you have the right tools, some experience, and a decent grasp of assembly language. It's only really annoying if you can't use a debugger.
All in all with 15yrs of training you can start the task :D
I've reverse engineered file types. But not actual code.
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).
Maybe this was bad advice, this approach is like trying to learn a spoken language by listening to a recording and looking up each word at a time. Probably it'd be better to get a deep understanding of how CPUs work in general, I can recommend the book Computer Organization and Design by Hennessy and Patterson for this. I agree with the other commenter that 15 years is more realistic so maybe just start by getting a 4 year degree in CompSci (and that book will probably be required reading).