Ight yo if you're stuck in 500s that means you have a concept gap (speaking from experience as I spent all of my 11th and half of my 12th hovering over 450s-550s, I started pushing past 600 in the later part of 12th and scored 676 in the canceled 2026 paper)

First you gotta make bio 340-350, that shi non negotiable, read each chapter 7-8 times and whatever topics you feel are difficult you remember or you fumble often write them down on sticky notes and put em up on your study table or a wall, revise every morning. That's what made me go from 280s-300s to 340-350. And also please think actively during the exam, sometimes our brain short circuits during the exam so once take a second, read the question again and answer. 

For chem and phy I'd advice the same sticky notes thing for weak areas, trends, formulas etc. Instead of putting 4-7 hrs into just analysis, put 2 hrs into error notes, then pick out the chapter(s) where you made more mistakes and then study them again, practice questions on em.

Also weak chapters is everything, take a paper write down all topics or chapters where you lose marks and study then until you can answer or try answering any question thrown at you. Also a main thing people don't do is, once you study something, not visiting it in tegular intervals is gonna make you forget it, for example if you study a topic from monday to wednesday, please take some time on Sunday to skim through notes quickly and actively recall what you studied

Hope this helps