Mathematics is a technique-based subject. Preparation for maths exams is all about 1. ensuring you understand the techniques and then 2. putting them into practice by working through questions.
But if you do not understand the techniques in the first place then you need to find help. Your first recourse for help will naturally be textbooks and your teachers, but maybe you need something more?
Sometimes even a one-off lesson with a tutor is sufficient to help you move beyond an impasse, raise your confidence, and boost your motivation.