Is it too late to start my revision now...?

I am a a grade 6ish student on average but have gotten 9s when cramming for my sciences. I want to be a grade 9 for all my subjects. Is it too late to start now? I've never actually revised, I've just crammed.

I don't know how to really revise with this short amount of time? Like what's the structure? What do I do? Do I try to go over the content and read the stuff I don't know but I don't really know what I don't know at the moment.

How do i plan the revision from now till gcses properly? What do I do??

Please help😭