Regex is very powerfull!
but can be somewhat hard to get a grasp at, at first.
Best way to start is to just make trials and errors, if someone told me that id still be in square one, its not always that simple to understand something without the basic knowledge of how regex works if you dont already know a regex guru.
but there is always ways to make the learning cruve way shorter and here is my answer:
Regex 101 is the absolute best way to make trials and errors with your regex while seeing realtime if it worked or not, after a while you will start to get the grasp of it all!