chances for improving grades in octnov

[Laibaaa]

I got a DDD in Alevel composite, hadn't given A1, gave composites instead.
im fairly bright, just had some trouble this session.
retaking all 3 composites this oct nov, how much can i improve? people say I wont be able to secure more than C's Please tell me chances for getting about a BBB this session please, Im very hardworking and willing to work very hard.
I have chemistry physics and maths by the way.

 

[Shin lol]

Math you need to know the concepts and than just start solving past paper directly , Physics is more likely to be a common sense point of view questions so you need to know the concepts but view the questions in the possible angles as much as you can and chemistry there is no other option than just studying the whole book and doing past paper