1. I was writing an exercise.
2. My sister was sleeping.
3. We were not doing an exercise.
4. Were you eating an ice-cream ?
5. They were playing volleyball.
6. What was your dad doing ?
7. Why were you crying ?
8. She was reading the whole evening.
9. Was your brother watching TV?
10. The sun was shining and the birds were singing in the trees.
P.S.: А вообще, тема легкая. Тебе нужно просто поменять глагол to be в форму прошедшего времени, то бишь :
am, is –> was
are –> were
Удачи ☺️