Here are the sentences based on the given words:

1. My mother went to Hanoi for business, and she has not returned yet.
2. You went shopping when I saw you yesterday morning.
3. This work has to be finished before 3 o'clock.
4. While I was doing homework last night, my brother played computer games.
5. We're going to buy a T-shirt for Paul's birthday.
6. What were you doing when I called you on the phone last night?
7. It's the most comfortable hotel I've ever stayed at.
8. They have not met my uncle since they have a job in Italy.