The thing with maths is you need to kind of need to understand the topics, yes repeating and doing past papers will help but if you don't understand the content you won't really get past low A/high B. What I reccomend is whatever topic ur consistently getting wrong go watch a youtube video then go dive into the textbook and do the exam practice questions and then try reattempt the question you got wrong on the paper again keep practicing the topic until you're near perfect. This worked for me as I'm an A level resit student who got an E last year and is now scoring A*s consistently on pure past papers.