Definitely worth relearning them because the first few topics are the base for the further ones, and they build on existing knowledge. Make notes or flashcards using a text book and maybe check out Cognito videos and lessons to help you learn the content, Maybe aim to learn a topic each week as it will be SO helpful as you progress in the course. Its better to do it sooner than later so you get the most out of your lessons and dont have to waste time learning things later!! Learn the content first but make sure to do past paper questions before mocks! Good luck