1. When I came into the classroom the pupils were discussing the plan of excursion. They had been already discussing it for 20 minutes.
2. When Olga finished the university her sister had been teaching English at school for 5 years
3. His parents left the apartment where they had been living for 20 years.
4. I was looking for my copybook for half an hour before I had been finding it under the newspaper.
5. When we left home it was raining. It had been already raining for two hours.