{Except sSunday, every morning, | Every morning except Sunday,} we need to go to our classroom from 宿舍our dormitory before 6:20am.

早上6:30以前到教室，还是早上6:30以前离开宿舍？

And at 7:30am. , we are allowed to have breakfast.

But I always don'tnever eat the food that the school makes.

After 10:10pm. , we will go back to 宿舍the dorm to sleep.

So repeatedlWe do this repeatedly, day after day.

So I use an mp3 player to listen to music 偷偷地.secretly.

Except sunday,everevery Sunday morning, we need to go to our classroom from 宿舍the dormitory before 6:20 am.

Every Monday morning is clearer because it acknowledges that this happens every single Sunday. Articles are required before the nouns 'classroom' and 'dormitory' (a place where students go to sleep at night when on the school campus).

AndThen, at 7:30 am. , we are allowed to have breakfast.

Adding 'then' is not required, but it helps the two sentences flow more smoothly. Also, it is not needed to place a period after '7:30 am', even though that is common with many English abbreviations (shortened phrases).

But I always don'tnever eat the food that the school makes.

The meaning of this sentence is a little bit unclear. If you meant that you don't ever eat the school food, you say 'never'. On the other hand, if you mean that you only occasionally eat the school food, you would say 'I don't always eat...'

Aftert 10:10 pm. , we will go back to 宿舍the dormitory to sleep.

Same punctuation correction. Additionally, the future tense (we will go) is not needed because your paragraph is describing something in a routine, that keeps happening.

So repeatedlyIt's very repetitive, and I usually feel tired.

Use 'repetitive' to describe something that keeps happening (and that is perhaps a bit boring)

I usually feel tired.

So I use mp3metimes, I use my MP3 player to listen to music 偷偷地.secretly!

Just one minor vocabulary change: MP3 player over MP3, since MP3 is the type of digital file, and MP3 player is the device on which you are listening to music.