Academic Comeback

Hi so like the title says I need tips on how to make an academic comeback. I wanna get the grades I need for uni and not be stuck on the grades I am now which are quite literally just fails. I need to actually learn how to study and how to rememeber and take in the information. I have resits for exams in September (chem and physics a level for year 12) and I wanna at the bare minimum, pass them. All tips would be appreciated thank you