first of all i am assuming you’re 5 months in to year 12, so swapping your course to something like maths or something wouldnt be that bad assuming you have prior gcse knowledge and are willing to spend extra hours outside of school catching up, you’ll obviously have to put in a lot of effort.
if you are unable to switch your course then dont worry, i started learning chemistry from scratch 3 weeks before my final exam. I was on a U before. So i spent 2 weeks learning all of paper 1. 3 days learning all of organic (paper2). and no revision for paper 3. I ended up getting an A.
How I prepared:
I watched Allery Chemistry on youtube explaining each topic
I made notes while learning from him
I then got on discord video call with 2 of my friends who were good at chemistry, together we went over the content and did some practice questions
I then attempted past papers to improve my knowledge and get to know the format of exam papers
lastly, i just memorised important stuff right before the exam
obviously i didnt do a lot of preparation so I scored an average of around 70% across the 3 papers, and ended up securing an A.
With chemistry I had to learn all of Maths and Further Maths from scratch aswell.
so dont worry i’m sure you’ll be fine. just lock in for the next couple of months you have lots of time