Ответ:

1a) (to) have some experience; (to) celebrate Christmas; (to) make a mistake; (to) do the shopping; (to) connect people; (to) get some trouble.

1b)

  1. We are a close family, and we always celebrate Christmas together. My favourite is Christmas.
  2. I didn’t make a mistake in the Maths test last week. So I’ve got an excellent mark!
  3. What can connect people from different countries? — A common project.
  4. My sister likes to do the shopping. She spends all her free time in shopping centres.
  5. If you take part in our project, you will have some experience in creating computer games.