There are lots of tutorials online on how to decompile an apk
There are also lots of tutorials on how to develop an apk


Now getting the source code is easy, making it work correctly is hard.
I have attached a dex to java decompiling tool with a bat script to help you build a Gradle for android studio.
is this perfect no, under no means. But it gets the job done, and one step closer to creating your own apps.
this tool has deobfuscation possibilities for those developers using pesky annoying tools.
By downloading you agree that you are knowledgeable with android studio how to get proper builds, versions, etc to generate the source to help you create a fully working application.
The posiblities are endless, start learning!!