With the app you can also flag the questions you struggle with, so there were some which were piss easy and I got right every time, but there were some that every time it cropped up I was like "tit I can't remember" so I flagged those ones so they appear more often and you eventually you'll remember the answer if you answer it often enough if that makes sense? For me personally there were about 10 questions which I could never remember and I just focused on those and made sure I always got them right and the rest were common sense.
I was so overwhelmed at the beginning when I started revising and thought "do I really need to read all this" there were some sections I definitely did need to read but generally what I kept doing is doing the mock tests and seeing which areas I was really weak on and I'd go and read that section.