Gcse aqa science struggles Watch
What really helped me was MyGCSEScience... his videos were free back when I did GCSES but I think now he charged £40 for access but trust me when I saw it's worth it. Also, CGP revision guides... treat them like your bible. Other than that, just repetitively do past papers because that's all GCSE science is... repetition.
I do Biology, Chemistry and Physics at A2 so if you're suck on anything in particular, just message me on here