Sure! Here are the rewritten sentences maintaining the same meaning:

17. This is the first time I have had such an exciting trip.
=> I have never had such an exciting trip before.

18. I haven't seen Anna for 10 days.
=> The last time I saw Anna was 10 days ago.

19. Today is Sunday. I haven’t taken a bath since Thursday.
=> It is Thursday since I last took a bath.

20. This is the first time he went abroad.
=> He hasn’t been abroad before.

21. She started driving 1 month ago.
=> She has been driving for 1 month.

22. I last had my hair cut when I left her.
=> I haven’t had my hair cut since I left her.

23. The last time she kissed me was 5 months ago.
=> She hasn’t kissed me for 5 months.

24. It is a long time since we last met.
=> We haven’t met for a long time.

25. This is the first time I had such a delicious meal.
=> I haven’t had such a delicious meal before.

26. I haven’t seen him for 8 days.
=> The last time I saw him was 8 days ago.

27. I haven’t taken a bath for a day.
=> It is a day since I last took a bath.