The most efficient way to find the problem and fix it is to find a string and start pulling it. Don't waste your time researching everything - you don't where that problem is yet.
You're either starting from "when I try A, B happens, but I want C" or you're looking at "the logs show this error (or just stop after last successful action)".
Use that as a starting place and follow it carefully until you get to the suspect behavior. Then start learning what's going and why it's wrong. Half the time, it's a red herring and you need to keep looking elsewhere.
It's take some effort to put on the blinders and ignore everything else, and you need to be OK with not knowing how some parts of the system work. If you need to know it to fix the problem, you'll learn about it in the course of your investigation.