How many hours should i study weekly? N26

Hey guys 141 days till my exam and im super duper stressed!

Just wondering how many hours should i study weekly because I dont think I study enough... I'm barely catching up although I study like 2-4 hours every day :(

I had really inexperienced teachers last year, so I have to relearn last year's Bio content...

HLs are: History, Economics, Bio; SLs: Eng Lit A, Chinese, Maths AA

We're in the IA stage now, so I can't make time to revise for my exams yet.

I'm aiming for 40 but im not sure if it's attainable because there's so much to revise and i'm on the verge of crying every day please help :(