As a start to your revision for the exams in May, you should revise the first 5 chemistry topics: Atomic Structure, Bonding, Quantitative Chemistry, Chemical Changes and Energy Changes.
Below are links to the specifications, BBC Bitesize revision website and, for each topic, a checklist & some questions (some of these “quickfire question sheets have a linked YouTube video).
Of course, if you want to continue and have a look at the other topics as well then that is fine.
GCSE Specification (first 5 topics)
1. Atomic structure & Periodic Table checklist
1. Atomic Structure & Periodic Table QuickFire Questions
2. Bonding, Structure & Properties QuickFire Questions
3. Quantitative QuickFire Questions