There are mistakes in five of the sentences. Find and correct

There are mistakes in five of the sentences. Find and correct them

1. We encourage all students doing some voluntary work

2. I've arranged visiting my grandparents on Saturday

3. I couldn't avoid hitting the dog as it ran out in front of my car

4. He considered to have a career in medicine but decided against it

5. She persuaded me to stay up and watch the film

6. My teacher suggested to learn ten new spellings every week

7. I can't afford to go out for dinner very often

8. He advised to have us an early night before the exam