If we learn by association, we remember by repetition. This is a powerful idea: the larger the number of problems that one practices, the greater the chances of achieving success in an examination. But also, a bit of advice comes to mind: practice every day. This has proven to be more effective than cramming all the material the evening before an exam.
Try to spend at least 15-20 minutes every day solving problems, but don’t miss a single date. Sooner than later, you will see the results!