I sense you're in a similar situation to me when I did my A-levels. Firstly, you likely know more than you think. But put that aside for now. Find a source of videos that goes through relevant content and try to understand it. My personal recommendations (may be old, I did this 4 years ago! They do post still though) are E.Rintoul and Allery Chemistry on youtube. Excellent and nice explanations for the knowledge and past paper questions