Here are the sentences transformed into reported speech:

1. He told her that she was his friend.
2. Johnny told his mother that he didn’t know how to do that exercise.
3. He advised me not to come back before one o'clock.
4. Mrs. Brown told her daughter to cook it in butter.
5. The pupils asked the teacher to give them better marks, please.
6. My friend asked if I was going to leave the next day.
7. My mother asked if I had done my homework.
8. I asked Bill what time he had gone to bed the night before.
9. Paul said that he had to go home then.
10. The policeman said that there was an accident.
11. The children said that they were waiting for the school bus.
12. Mr. Brown asked if I had to go then.
13. Tom asked if I was going to visit my aunt the following day.
14. The teacher told his students to listen to him and not to make a noise.
15. Mary told Helen that she was tired of eating fish.