Hmm....
I write many things on it..
But I usally write about my school exam now days because soon there will be a mid term exam...
That's bad:(
I write down about what I have to study, and what I studied

If your heart becomes wise, then my own heart will rejoice.​—Prov. 23:15.

=

I write many things on it.
But I usually write about my school exams nowadays because there will be a midterm exam soon.
That's bad:(
I write down what I have to study, and what I have studied
 

= "nowadays" means "these days" or "in the present time"
= "write down" means "to record something"
= "I have studied" is better for the sentence because it is still related to the present
= You did fantastic with your sentences~