Here are the rewritten sentences:

1. "Where did you meet him?" Jimmy asked.
- Jimmy inquired about where he had met him.

2. "When should I register for the new course on Chinese?" Jim asked his teacher.
- Jim asked his teacher when he should register for the new Chinese course.

3. Joana couldn't decide when she should start her journey.
- Joana was uncertain about when to start her journey.

4. "You must stay in bed until next Monday!" the doctor said.
- The doctor instructed that she must stay in bed until next Monday.

5. I have no idea who I should call for help in this situation.
- I don't know who I should contact for assistance in this situation.

6. "Should I tell her the truth about her misery?" she asked herself.
- She questioned whether she should reveal the truth about her misery.

7. I'm not sure what I should do to help her overcome her mom's death.
- I am uncertain about how to assist her in coping with her mother's passing.

8. "I am going to work for a new company next week," John said.
- John mentioned that he would be working for a new company the following week.