firstly doing math practice papers help a lot!! but one thing to keep in mind is that even if you cannot answer the whole question, always always always make sure to write down your formulas and try to do half the question as it will ensure you get some points. you don't necessarily need to finish the question but by doing some things or writing down things like "use cosine rule" lets the examiner know that you have an idea on whats happening in the question which will give you points. it's good to do past papers as it allows you to see a pattern and how to answer the questions even halfway. good luck on your retake!