1) Have you done your homework? - Yes, I have just finished
2) Are your brother playing computer games now? - No, he is reading a detective story
3) What will you do tomorrow? - I will visit my granny / What are you going to do tomorrow? - I am going to visit my granny (на твоё усмотрение, какое выбрать)
4) Are they go to school on Saturdays? - Yes they are, they have five lessons
5)Did the students take part in the competition yesterday? - Yes, they won the competition.
Вроде так.