Ответ:

  1. We have got a lot of newspapers, but we have got a few magazines.
  2. Will there be a new bookshop here?
  3. I am sure he will be at school tomorrow.
  4. It doesn't rain in February.
  5. I think I am going to have a birthday party on Saturday. (Предложение составлено правильно.)
  6. Once upon a time it was a prince who wanted to find a magic apple. (Предложение составлено правильно.)
  7. Those firemen are very busy today.
  8. He has had this car for ten months.
  9. I didn't want to meet that postman so I had to leave quickly.
  10. It isn't going to rain. You needn't take an umbrella.

Примечание: в предложениях 5 и 6 ошибок нет, хотя условие утверждает, что ошибка есть в каждом номере.