Hey Lilyan!
I honestly understand your worries so much, that was me last year! With regards to you upcoming SAC - I would write down everything you need to know for the sac (go through the study design and break it down into really simple small sections for example the first dot point of outcome 2 can be broken down to:
- sources and modes of transmission of plant and animal hormones
- sources and modes of transmission of neurotransmitters
- sources and modes of transmission of cytokines
- sources and modes of transmission of pheromones
and from this you can create a A5 summary for each small topic or create a mindmap, and revise it daily or using spaced repetition and do checkpoints or flash cards or something else that uses active recall. I also would recommend asking your teacher for a practice sac so you can see how you perform under timed conditions and really iron out areas of weakness. Ultimately we are studying for the exam so don't get to down about your sac marks (they are important but dont dwell on what could have been)
You may also find these useful
Tips for Bioconquering bio - 50 in year 11Best of luck and I hope this helps
EDIT: Also don't listen to your friends, everyone's perception of 'not studying' is very different for me not studying is barely doing anything
for example: usually study everyday/every second day in the 2 weeks leading up to a sac and therefore for me no study is only doing a little bit the night/or two before.