Olevels cooking me

Hi does anybody have tips for studying for olevels just for core subjects😭
My emath failed and my sci (chem/bio) is always a borderline fail for chem and I usually only pass bio by 5-10 marks, my Eng is also very uncertain cus my results can fluctuate from a2 to b4
I take hist/ss as well but my results also tend to fluctuate so I’m not certain on that as well