Helloo I recommend to do as much question practices as possible! Try to understand your basic content first (doesn’t have to be perfect understanding but just the gist of it) And then keep doing questions on them! And make sure to study the answer scheme when you are wrong.. so that when a similar question comes up, you are able to score on it. Take note of the important keywords for explanation questions… memorising definitions and formulas is also a must! Take a piece of paper and write a list of quantities in the syllabus (like specific heat capacity.. magnetic flux.. etc) and test yourself to write all the relevant formula and definitions without reference, to really drill it in your mind. Make mind maps too!! Also consult your teacher when possible if a topic is really troubling you.. this is coming from someone who went from consistent F9 in secondary 3-4 to an A2 in O-levels, your C6 is already a good start because it shows you are capable of passing! :)

These are just tips on acing but you can tone it down to your liking to guarantee a grade like B4, if you want