Мне . надо написать школьные правила и там должно быть слово mast и mas not

Во-первых must и must not.
1) You mast do your homework
2) You mustn’t make noise
3) You must listen to your teacher
4) you mustn’t talk to your classmates on the lesson
5) You mustn’t use your mobile phone on the lessons
6) you must study hard
7) you must wear a school uniform
8) You must come to school on time

It's not a secret that I like to get presetnts, like all teenagers of my age.

Firs of all I'd like to say that giving presents is more pleasant for me than get it.

But I'm going to speak about present what i would like to get. So I've got an interesting hobby. I like solving brain teasers. I've got many of them in my home collection.

The first time I have seen brain teaser was then I was 11 years old. One of my older friends had fond of solving Rubick's Cube.

I'd tried to repeat after him. But I could not do it like he. Then I started surfing the internet, to find a sollution of Rubick's Cube. And I found it.

Some days later i'd learnt how to solve it. Now I've got my personal record. 23.64 sec.

To conclude I'd like to say, that I hope to get Rubicks Cube 4x4 from my parents. 

My name is Natasha. I’m twelve years old. I’m in the fifth grade. I study at gymnasium school number 1 in St. Petersburg. My school is the best. My school is a four-storeyed building. Pupils of primary school study on the ground floor. There is a big gym in our school. Our physical training lessons and different sport competitions are held there. We celebrate holidays in assembly hall. All classrooms of our school are light and spacious. There are physics and chemistry labs where we can make experiments. There are new computers in the computer sciences room. Our pupils often win the city academic competitions. Teachers who work in our school are very good. Each of them teaches well and their lessons are quite interesting. Our form-mistress’ name is Irina. She is a teacher of Russian and literature. Thank to her our class is united and exemplary. I and all my classmates often go to the cinema, theatre, museums and exhibitions. During summer holidays I miss my school. I like my school very much.