​Find and correct the mistake: He was seen go to the beach and some other people. I discovered that many change things were happened last night

​Find and correct the mistake
1. He was seen go to the beach and some other people
2. I discovered that many change things were happened last night
3. He's believed to work for the CIA in 1970s
4. We're not let to cycle in the park, are we ?
5. You should get your car to servise every 2 years
6. Only coffee and dessert been server at reception yesterday
7. When I have been finished my work, I'm going to take a walk
8. Because we have a writing agreement, he won't be able to rise our rent for 2 years
9. The heel of my shoes broke off and than my dress get tore in the elevator door
10. When I crossed the road, I saw two men whose car was broken down