heyy!
I did AQA English so unfortunately can't help with timings cause I'm not sure how marks are allocated etc
But for higher maths, I'd say do practice papers. If you get to a topic you don't understand or you get a question wrong, watch videos on it and do lots of practice questions on that topic to ensure you get it (First-class maths and PMT have good stuff). Keep doing that until you get it right
I'd say the same thing for bio and chem too. For topics you don't understand or questions you get wrong, watch videos and do practice Q's on that topic only until you get it right.
In bio and chem, they often want specific and formulaic answers, like for titration experiments in chem, so I'd look at the markscheme and just rote learn the correct points to make to get the marks. Also, oftentimes there are specific keywords they want you to include, so whenever you get a question, take a second to look at it and thing of the specific words they want you to include to get the marks, e.g plasmic in genetic modification in bio
Hope this helps
