Grammar exercice correction?

Hi everybody

I have an grammer exercice, and I want to know if what I wrote in blue is right in the sentences.

1. Which of these three jeans will you buy? The cheaper one.

2. He is used to drink coffee for breakfast.

3. I wish I would call her earlier, it is too late now.

4. Do you remember seeing this child before?

5. I suggest he will be going tomorrow.

6. When I went to China last year, it was the first time I have seen so many people in the streets.

7. They have known each other for 3 years when they got married.

8. I hope you do not mind that I leave tomorrow.

9.She made much less mistakes than I expercted.

10. I would rather you did not go to such a dangerous place.

11. The prisoners, half of whom where serving long-term prison sentences, finally returned to their cells.

12. Where did you have your car washing ?

13. If you had come earlier, we would have got a better table.

14. She would better do it now.

15. You are looking forward to visit this city!

16. Even they tried very hard, they never succeeded.

17. Should she call, please tell her I will be back later.

18. The new 'red' cars will produce twice less carbon monoxide than yesterday's models.

19. It is high time Spain and Portugal to settle their differences and to begin working together.

I hope you can help me to see and to mark my mistakes.

Thx a lot!