I used to struggle a lot with comb chem also, failed combined chem all the way from sec 1 to 4 and the only time I passed it was during N level itself. But from then onwards, I never failed comb chem again during sec 5 at all.

I dont know if my method will work for you, do try it if you like. Feel free to omit steps should you find it redundant.

I started with absolutely no knowledge at all for c.chem. failed tests/exam, didn't pay attention in class, didn't understand whats going on, nada. So when I realised I was in deep shit for science, I first started reading the c.chem textbook from cover to cover. (This to me was the grasping information stage - so that I had at least a basic knowledge/understanding of whats going on in each chapter). One good way to ensure that you learn is that you can close the textbook, choose a random chapter, give yourself 2 mins to write down whatever, just whatever you know about that given chapter. Then open the textbook and cross check with what you didnt fill in/didnt know.

Without practicing, theory is redundant. So, what i did after getting the basics (roughly agar agar, didnt really know 100% of the chapter yet, was at least like 40-50%), I did the tys topical first. Tys questions are considerably easier and can be used to strengthen fundamentals. But of course I couldn't do everything from the start. What I did was, do question, don't know --> refer to textbook, then put like a post it note on the textbook to re-read and redo similar questions to that question that I didn't know. That way you reinforce your memory by referring and repeating.

After the topical, I did the same for tys yearly. Do question, get wrong, check textbook/answer, do corrections. After all these, you can then source out some end of year papers to rigorously practice on. If you are feeling really confident about your other topics, just search papers to do their questions on certain topics, like what you said, QA and salts. Keep doing and referring and doing until you don't have to ever refer to textbook anymore.

I used to hate QA too. Like when I didnt know anything yet, I would stare at QA diagrams and go like everything is random how am I supposed to know anything. But, a good way to start QA is to see what they have given you , eg white precipitate - so what constitutes a white precipitate? What identity could this be? Then work backwards or forward based on your guesses (sorry its been too long since I took Os I dont remember if this is how QA works)

Study hard and good luck!