Here are the sentences rewritten in reported speech:

1. She said to him, "Please turn off the lights."
- She asked him to turn off the lights.

2. He said to his son, "You should study harder for the exams."
- He advised his son to study harder for the exams.

3. She said, "I'll help you move tomorrow."
- She promised to help him/her move the next day.

4. The manager said to the employee, "You must complete this task by tomorrow."
- The manager ordered the employee to complete the task by the following day.

5. She said to her friend, "Please wait for me here."
- She requested her friend to wait for her there.

6. The doctor said to him, "You should take this medicine twice a day."
- The doctor advised him to take the medicine twice a day.

7. She said, "I'm sorry. I'm late."
- She apologized for being late.