For maths and English language, once uve learnt everything u just need to practise using practise papers/ questions from online
For English lit, read thru the book/text, pick out key quotes and write them down, then annotate them (and revise this) - this massively helped me in achieving a grade 7 (A)
Also, use mr bruff on youtube and make flashcards
Also, it's not too late, it's actually the perfect time...I've also just started revising by making flashcards
If those are the only subjects ur doing then ull definetly be fine