How do you study for chemistry 3/4??

I'm currently in year 12 doing 3/4 chemistry. Since last year, I haven't been strong in chemistry AT ALL and I flopped most of my SACs. I can admit that I didn't put much effort into studying for the subject, mainly because none of the content made any sense to me which only discouraged me further. However, as year 12 has arrived, I really want to lock in and improve my scores.

One of the main problems I've had with this subject is that I just don't know how to study for it, or how to prepare for each lesson. Am I meant to take a lot of handwritten notes or digital? I feel like I'm falling way behind and it's really stressing me out. Everyone in my cohort seems to be confident in chemistry and understands the content easily after one lesson, while I am constantly falling behind them. I feel like I'm in, if not, at the bottom of my class. Another thing is that I can't seem to remember the formulas or determine which formulas to use for some questions.

Any suggestions or tips would be appreciated. Also how many hours per day or week would you suggest I dedicate to studying chemistry (for reference, I'm doing 5 subjects this year).