View executed code while running / debugging an app


Hello everybody, I am very new to android studio and app development in general. I am working in a project which already has developed an app with a lot of features. I shall improve certain features and therefore I need to understand which files and which code are executed at which point in the app. Since there are a lot of different files with complex code, I was wondering if it is possible to see which code (or file) is executed while running/debugging the app?
I read that I could use breakpoints, however it is quite difficult to even find out where even to put the breakpoint if you do not know which file is executed for which feature. Do you have any ideas what I could do?

Best J :)