Pure Maths: C1-C4 and Chemistry

Hi, I hope you're all well.
Quick question; is it possible for me to 'up' the scores I get in C1-C4 (AQA)?
I normally get around 65+ out of 75, but I'd like to be scoring 100% or thereabouts in raw marks. Seeing others scoring that high also puts me under pressure.

C2 and C4 are probably my weakest.
I can tend to get around 71/75 in C1 and similar in C3.

Days left until exams:
C1 - 20
C2 - 27
C3 - 48
C4 - 50

Is it possible in this time span?
And if so, any tips?

Also, I mark quite harshly when I do past papers. Yet, when I do these same papers in college, my mind just goes blank and scores lower.
I don't understand why?
In college exams, the papers seem foreign even though i've done so many past papers and when we go through them the next day, I feel like a complete idiot.

And if anyone does chemistry (OCR), any tips for that would be greatly appreciated too.
Thanks!