You have to go back on whichever topic you’re stuck on; do more of these questions from the text book until you’re fully confident on how to answer the question.
What exam board do you do for maths?
No problem. Just try finding that topic that you don’t understand in the textbook, try and answer more of these types.
If you don’t understand the general concept, you could search the topic on YouTube and there are lots of explanations on there.
If it’s like Bionomial expansion then just type in A level Bionomial expansion CAIE on YouTube, but If nothing comes up then type in Bionomial expansion A level, a lot of content overlaps from different exam boards.
Just do lots of these question types from your textbook. Then once you attempt the question, you can check the answer which is normally either at the very back of your book or if it’s not then type in your exam boards textbook on google and see if you can find answers.
Once you’ve done all this, do another past paper and then just keep repeating until you’ve understood everything. Make sure you actually take the time to understand all the concepts before doing a full past paper though, it makes your life easier.
And also make sure you try attempting topic by past papers for you exam board - just type in “CAIE A level maths topic by past papers” on google and you should find something, if not then just focus on perfecting the textbook questions before you move onto full past papers.
Good luck with your revision.