It can be very confusing, as someone who isn't very strong with it, I would say practice is going to be your best friend. Also simplifying things as much as possible goes a long was. Taking whatever complicated variables they throw at you and boiling them down to A, B, and C can be massive for understanding complicated questions.

I would say try to give yourself appropriate breaks in between sections, or try doing some sections instead of full practice tests when studying to try to build stamina