I　went to Tokyo Disney Sea with my friend!

I went to Tokyo Disney Sea with my friend in Friday. In Friday, A School that I'm going was holiday so I could go there. We played a lot of attraction and saw 2 shows. Everyting were very enjoying. Most enjoying attraction was Center of the Earth, witch is a attraction like Roller coaster. We walked very much so we were tired, bat we enjoyed there very much! I want to go there again with my friend.

Firstly, great job. It it more that I can do in Japanese.

...Sea with my friend (on) Friday. 

A School that I'm going to was holiday so I could go there.

this sentence is a little awkward. It would be better to say "The school I attend had a holiday that day, so I was able to go.

We played a lot of attraction and saw 2 shows.

We visited a lot of attractions and saw 2 shows.

Everyting were very enjoying.

Everything was very enjoyable.

Most enjoying attraction was Center of the Earth, witch is a attraction like Roller coaster.

The most enjoyable attraction was the Center of the Earth,...

...witch is a attraction like Roller coaster.

the witch you used here means (majo 魔女). The one you need is which. We do not need to say attraction again so it should read. "...which is like a roller coaster."

We walked very much so we were tired, bat we enjoyed there very much!

We walked a lot so we were tired, but (demo でも）we enjoyed it there very much!