Here are the verbs in the correct form:

1. Let's have noodles with beef or chicken.
2. I hate doing the same things day after day.
3. Volunteering is very special to many people.
4. It's difficult for me to play the cello.
5. What is the price of a bowl of beef noodle soup?
6. Truong started recycling rubbish three years ago.
7. You'd better focus on your studies.
8. Unfortunately, I made a few mistakes in my last exam.