Heyy, you seem like you are doing really well so far so well done.
I totally understand what you mean, I completed my GCSE’s last year and motivation to study was definitely hard, especially in the middle of the exam season when you start feeling burnt out. Therefore, I think it’s really good that you’re starting now because time will fly by. Try to get organised now, have notes for every subject separated. Personally, I made kind of cheat sheets where the material of a paper was condensed onto a A4 page it was a mini challenge to see how much I could fit and made sure to include all key words and phrases I knew would get me marks - I would read this just before the exam as a refresher and quick dump.
To keep me going and it may seem cringe but I always pictured my end goal - opening my results and seeing straight 9’s and that emotion is what kept me going. Or picture someone thinking you can’t do it and prove them wrong.
You seem to have your STEM subjects nailed and these are definitely most important. I used physics maths tutor to do all the exam questions and past papers, maths genie is good for maths and for L2 further maths I used a website called first class maths and watched every video and did every worksheet there and I found that helped.
I struggled revising for English personally because I didn’t really enjoy it. For literature, closer to the exams I went through past papers to see the probability of the topics that could come up and which poem could potentially come up. I then for every theme/poem/character made sure I could think of 3 quotes and come up with a quick analysis. I prioritised those most likely to come up and it meant in my exam I had ideas in my head already because it was one of the themes I had practised.
Also try to find a general structure to your paragraphs so you don’t panic in your exam - topic sentence introducing theme of text, quote, 1st interpretation with a method, alternative interpretation, zoom in one a word, what was the authors intent in context with the time, why does this relate to the question… for example. Try to find unique interpretations even if it feels like you are spewing lies and it feels ridiculous. What exam board/ texts are you studying?
For language, I was a fast writer so I burst out as many paragraphs as I could per question and our school actually preplanned a story which we memorised and tried to fit to past exam questions. We then practised adapting this to different questions but it meant our grammar and punctuation scored pretty high.
This was kind of a rant but I hope it helps in some way and good luck!