Do this, find you syllabus for that course, usually online and go to those sections. Work through each of them finding alot of questions for each point stating what you need to know.
If its actually the knowledge side of things there are plenty of you tube videos covering angles and parallel lines.
As you doing higher there will be some As-level content which is where i feel your difficulty may be.
Exam solutions is a good place to start.
Hope it helps