Sure! Here are the rewritten sentences:

1. She has been working as a secretary for five years.
2. We have been cooking for the party for four hours.
3. We started.
4. Samuel has been keeping a diary for fifteen years.
5. We have been living here for fifteen years.
6. Minh has begun collecting stamps in 2011.
7. I have started working for the company a year ago.
8. John has been playing the piano for ten years.
9. They started investigating the case a week ago.
10. John has been learning English for three years.
11. John started working two months ago.
12. We have been working for this company for two months.
13. The last time it rained was a fortnight ago.
14. It was.
15. She has not seen her friends for five years.
16. It has been.
17. The last time I saw him was when I lived in London.
18. I haven’t seen him since.
19. I last saw her when I was a student.
20. I haven’t enjoyed myself so much for years.
21. It is.
22. It started to rain at 2 o’clock.
23. It has.
24. He has bought that luxury car when he left school.
25. This journey has been tiring.
26. It is.
27. A local mechanic has repaired our car.
28. We have.
29. In spite of our efforts, we failed.
30. Although we tried.