Hours of study in IB ?? Watch
How many hours a week should a person be studying in IB
SL AA maths
However, regarding you taking HL Biology, I definitely recommend spending a lot of hours and time on that, memorising, revising and learning the new content. It is heavy in information, and therefore, you really must spend a lot of time on it.
Only reason I am giving advice on bio as it is the only class I also take.