Here are the correct forms of the verbs for the sentences provided:

1. She is sad because her son does not visit her very often.
2. Hoa comes from Hue, but now she lives with her uncle in Ha Noi.
3. I’m busy at the moment. I am decorating the living room.
4. We have lived here since I was ten.
5. Because Minh never works for a charity organisation, he really wants to do it.
6. She has been to Sa Pa many times.
7. Do you hear what she just said?
8. Lan moved to Ho Chi Minh two years ago and I have not met her since then.
9. Peter bought a new CD player yesterday, but I did not see it yet.
10. Frank did his homework, then he listened to music.
11. I did not study hard last year.
12. Where have you been last night? I phoned you but no one answered me.
13. When he was young, he could speak English well.
14. Next week we will have many kinds of examinations. It is going to be a very busy week, I think.
15. He will phone us before he leaves home tomorrow.
16. I hope I will be on time for the meeting.
17. I see John at 8 o'clock tonight.
18. Students are interested in playing computer games.
19. I’m tired of having nothing to do at home.
20. How about going to the zoo this weekend?
21. He left without taking his coat.
22. Every girl should learn how to cook.
23. I prefer walking to riding in the garden when it is fine.
24. Lan enjoys sitting in the garden when it is fine.

Feel free to ask if you have any more questions!