First things first, try not to panic! Other than modern studies, you have some amazing results and with the right amount of effort everything will work out fine. You’re not the only one in this position, and it’s extremely common to see people go from Fs to As.
My main advice would be to create a revision timetable that focuses majorly on the subjects you’re struggling with, for example do some revision for modern studies every other day, also prioritise ruae and biology revision, and focus less on the subjects you’ve got an A in.
I didn’t take modern studies but I took history and what I did to prepare was creating my own summary sheets of the content (bullet points, mindmaps etc), putting them in flashcards/making myself actively recall the points, making sure I knew the techniques to answer all the different question types (explain, describe etc) and pulling everything together by doing a LOT of past paper practice. If your teacher is willing to mark your work for you, that’s great, if not try to mark it while looking at your notes of the content and answer techniques. The best way to learn is to identify areas where you’re struggling and act on them.
RUAE is sooo difficult, it was definitely the hardest area in English for me. Again, it’s all about technique, and some papers will naturally be harder than others. The best course of action is to do practice questions, look at the mark scheme/get your work marked, and see what you could have said. English is kinda good though in the sense that if you’re weak in one area, you’ve got many others to rely on (portfolio submissions, TA, essay).
With biology, active recall of the course content helps a lot because that’s what you’re assessed on the most. Making flashcards of the course specification helped me a lot. You must also be familiar with diagrams and how to label them. If you don’t own a textbook already, it’s a great investment, as you have all these things and they also teach you how to interpret graphs, do maths calculations etc.
Don’t expect to perfect everything overnight, it’s a gradual process, but with every revision session you’ll improve. Don’t stress yourself too much either, be sure to take loads of breaks and take care of your mental health.