[Help] [Q] Developing a xposed module

So i want to start building a xposed module that is used for notification behavior (always expand, ect)

Was just wqondering what is the best peice of software to write this stuff out and what language is it in?

P.S can i pick i use code from a git hub (give credit of course and ask for permission first) from a rom and turn that one function into an xposed module?

any help would be amazing