Boring dDay

I'm going to write about my day, so(, here goes)...

This flows better and is more natural.

I woke up too late because I couldn't sleep yesterday, and I arrived at the school and Iwent took my history class, but it was boreding.

I am bored, it was boring

I had my breakfast at 9 am with my friends, and we also studied for our math exam, but we didn't have it(it was postponed / it was canceled).

I woke up too late because I couldn't sleep yesterday,last night. I arrived at the school and Iwent took my history class, but it was boreding.

"bored" is an emotion people feel
"Boring" is an active to describe an experience.

I had my breakfast at 9 am with my friends, and w. We also studied for our math exam, but we didn't have ihaven't taken it yet.

I woke up too late because I couldn't sleep yesterday,. I arrived at the school and Iwent took my history class, but it was boreding.

It's more common to say: "I went to school" (:

I had my breakfast at 9 am.m. with my friends, and we also studied for our math exam, but we didn't have it.

For better clarity, I would say why you didn't have the exam. Was it cancelled or was it scheduled for a different day?