Hi. I achieved straight A's at Nat 5, so hopefully I can build on what's already been said and help.
One thing about biology, business, and geography is that they are all centered around memorisation more than anything else.
Firstly, I would like to explain the difference between passive revision and active revision because if you've primarily been trying to do passive revision it might explain some of why you're struggling.
Passive revision is things that don't really boost your knowledge of the content in the long-term, such as re-reading and highlighting your notes.
Active revision is harder but more effective as it encourages you to recall what you already know. This can include making mindmaps, blurting, flashcards (so long as they are question and answer flashcards rather than just your notes), explaining the content out loud, and past papers.
Blurting is when you write down everything you can remember about a topic without help from your notes. Then, once you written what you can remember, you check your notes and write down anything you forgot in a different colour pen. Some people like to read over their notes for a topic before blurting as a little re-fresher.
You've said that you give up quite easily with flashcards, so I suggest that you maybe take a more interesting approach to them (as, let's face it, they can be quite boring). What I mean by this is by making a revision game (for example snakes and ladders). Each square can have a question on it, and you can't move on until you've answered the question correctly (you need to make an answer key for this). You can do this with other games too, but I've found snakes and ladders to be the easiest to make for revision.
If you're someone who learns quite well by listening, I suggest you find some YouTube videos, podcasts, or even put your notes into an AI podcast generator if you can't fund anything good already out there. This is technically passive revision, but it can be helpful if you do it often (e.g., listen to a video/podcast episode when walking to and from school).
Lastly, past paper questions are important, but it's best to wait until you understand the content more to do them.
I hope this helps, and if you have any more questions, feel free to ask me. 😊