1)O verbo modal must é usado para dar intensividade tipo: you must study - voce deve estudar. E o mustn't é o negativo.

2)O futuro imediato na forma negativa é para expressar um ato que voce nao vai fazer no momento.

3)
She is going  to talk with the his brother after school.
My mother is gonig to buy a new car.
I'm very sad! My best friend, is going to onother city
My neighbors are going to build a new garage
My friend and i are going to learn italian
We are going to buy a new book tomorrow
I'm going to work in my gardem
Vlad is going to live in England
Sara is going to write a book
We are going to speak spanish at school

4)
She is going to kiss your boyfriend
They are going to play soccer in the camp
We are going to talk in spanish in the school
I'm going to clean my room
He is going to study a lot

5)
They are going to the mall with me
He is going to drive the truck
She is going to watch a movie tonight
I'm going to play tennis with my friends today
We are going to study math in my classroom

6)
I'm not going to to have a dinner with my parants
Sara isn't going to go to school tomorrow
They aren't going to move to Rio next month
The girl isn't going to buy a magazine
Danny isn't going to eat sandwich
The girls aren't going to cross the street
Poul isn't going to swim in the river
My friend aren't going to play football
Billy isn't gonig to take the bus
Paty isn't going to see the doctor today