1. When I left the house, I realised that I had forgotten my keys.
2. After I had finished digging the garden, I decided to go for a walk.
3. I lent Fiona some money only after she had promised to give it back the next day.
4. They kept arguing about the money their father had left them in his will when he died.
5. Kate started studying after John had left.
6. I bought Becky a plant yesterday, because she had sung (или просто sang) so well in the concert the night before.
7. When I saw Julie, I realised that I had met her before.
8. She went to bed after all her guests had left.
9. She was very depressed, because she had lost her job.
10. He had left by the time I got there.
11. Mark went home after he had finished his work.