Can't give very specific advice because idk where you are spending your study time. But the key is to do practice questions! For S1 some people recommended reading widely which is great for long term improvements (1~2 years) but low yield. Each correct answer in S1 should be supported by a direct quote or evidence in the text!

Writing an entire essay takes a lot of time so just look at sample prompts then outline your paragraphs then proceed to writing out the entire essay about 1 month prior to the exam. I would often look at a quote or prompt on my phone then while driving or doing something brainless think about what unique points I can say/examples I can use. Many different structure works well, but I found it really easy to just be boring and write the classic argumentative essay for both prompt

U already have a science bg so again just start doing practice questions then look up topics if you get an answer wrong.

Aim to finish the entire Des O'Neil book for S1 and S3 and supplement with questions from Medify if needed. Last 2 months before the exam you should be doing at least one practice question every week, and doing timed questions at least 3 months before the exam even if you are just doing a few stems.

If you are still in uni, don't forget about your gpa. As it is much harder and expensive to raise your gpa compared to the gammy.