Hey!
I felt similar to you a few years ago, and I felt like the best method for me a) watching YouTube tutorials such as examsolutions for maths
B) doing loads of past paper questions to see exactly where I needed help! If you go on physics and maths tutor I believe you can find them organised by topic. Now I know you might think that all the questions will be too hard/ there’s no point in answering things you haven’t learnt about properly, but if you revise with the questions (e.g start off by doing physics with the textbook to help/ do maths questions and ask a teacher/watch a video about ones you can’t do) then you’ll get much more used to exams and it will hopefully improve your grade. Exams do tend to repeat patterns in some questions. Eventually it would be good to start doing whole papers under timed conditions.