8. Nancy hasn't come here since 1986.
9. this is the first time I've been to Japan
10.  When did Helen and Robert get married?
11. We haven't had a conversation for a long time
12. Thanks, but I've already eaten
13.  I have never read such an interesting book before.​

8. The last time Nancy came here was in 1986.
-> Nancy hasn't came here since 1986.
9. This is my first visit to Japan.
-> This is the first time I have visited Japan.
10. How long have Helen and Robert been married?
-> When did Helen and Robert get married?
11. It's along time since our last conversation.
-> We haven't spoken in a long time.
12. Thanks, but I had something to eat earlier.
-> Thanks, but I've already eaten earlier.
13. This is the most interesting book I've ever read.
-> I've never read a book this interesting before.
14. This is my first game of water-polo.
-> I've never played water polo before.
15. When she heard the results, Mary began to feel more confident.
-> Since hearing the results, Mary has begun to feel more confident.