IELTS Grammar: correct the mistakes

Here are some sentences that people wrote below yesterday's speaking lesson (about 'collecting'). Can you find and correct the mistakes?

1) There are a lot of things that people often are collect.
2) I think people often go to gather small things such as stamps.
2) Whenever I went in a vacation, I used this opportunity to buy another object.
3) Let me think, may be valuable watches which their prices increase by time.
5) People collecting things for many reasons for example they do it as a hobby.