Rephrasing

I was doing some rephrasing exercises and wanted to know if my answers could be correct. The sentences in bold are supposed to be the correct answer (answer key).
Could you help me out? If you also could explain me why my sentence isn’t correct that would be great =) Thank you in advance!

1. The last time Nancy came here was 1986.
Nancy hasn’t....
Nancy hasn’t been here since 1986
Nancy hasn’t come here since 1986

2. I haven’t been to an Indian restaurant for ages
It’s ages...
It’s ages ago that I have been to an Indian restaurant
It’s ages since I haven’t been to an Indian restaurant

3. This is my firts visit to Japan
This is the firts...
This is the first time That I’m in Japan
This is the first time I have visited Japan

4. How long have Helen and Robert been married?
When...
When did Helen and Robert marry?
When did Helen and Robert get married?

5. She has never been to the club before
It’s...
It’s the first time that she is in a club.
It’s the first time she has been to the club

6. She has never heard sucha a funny story.
It’s...
It’s the first time that she heard such a funny story
It’s the funniest story she has ever heard

7. It’s the worst headache she has ever had
She’s...
She’s having her worst headache ever
She’s never had such a bad headache

8. When did she come back?
Since...
Since when is she back?
*Since when has she been here?*

9. I haven’t spoken to him for a week.
The last...
The last time I’ve spoken to him was last week
The last time I’ve spoken to him was one week ago

10. I’ve never heard such a silly story.
It’s....
It’s the first time that I’ve heard such a silly story
It’s the silliest story I’ve ever heard

11. When did you last go to London?
When was...
When was the last time you’ve been to London?
*When was your last visit to London?*

12. We’ve known them since 1992
Since when do you know them?
*Since when have you known them?*

13. I was my hair three times a week.
How many times a week do you wash your hair?
*How often do you wash your hair?*

14. Try to finish your homework so we can go for a walk.
If....
If you finish your homework early we can go for a walk
If you finish your homework early we will go for a walk

15. We didn’t miss the plane because we left early.
If...
If we hadn’t left early we would have missed the plane
If we handn´t left early, we wouldn’t have missed the plane

16. It’s a pity you don’t work more efficiently.
I wish...
I wish you would work more efficiently
I wish you worked more efficiently