Some of these sentences aren't right. correct¹ them 1) i don't know if mike will stay with us or not. 2) if she will play the game ,she will win. she's very good at tennis. 3) these children will be seven when september comes. 4) we won't go skating if it will be very cold. 5) i'll call you as soon as the film will be over.

1) I don't know if Mike stays with us or not.
2) If she plays the game, she will win. She's very good at tennis.
3) These children will be seven when September comes. (верно)
4) We won't go skating if it is very cold.
5) I'll call you as soon as the film is over.