excersice

please i need you with following questions.

Q- Are you taking a lot of classes these days?
A- I -------- (take) just two: world geography and physics. I ------- (have)
a full-time job, so I --------- (not/have) a lot of free time.

Q- How often -------- you --------- (go) to the library?
A- I -------- (go) every saturday. but I -------- (study) at home a lot, too.
I ----------- (prepare) for an important exam.

So which tense we use and why.
so many thanks