literally just do the exam questions ull find that the questions are ridiculously repetitive. the only tricky things are mabey the calculations. but the theory is easy to well in if you just keep doing questions.
Exam papers are essential, only reason I'm doing well in Chemistry is because my teacher has been giving us exam questions since the very start of 5th year. Learn off the definitions and answer your best part of the question first, whether it be theory or a calculation, as this will help build your confidence. The course is also quite short, for my class we will finish the course before St. Patrick's day. Most people will have a good 2 months of pure revision, or to understand a section you never really got. So don't lose hope yet and definitely don't worry too much about the mocks, they will not be a good indicator.