Поставьте глаголы, стоящие в скобках, в Past Simple или Past Perfect.

Поставьте глаголы, стоящие в скобках, в Past Simple либо Past Perfect. Пожалуйста.
1. I (to know) that he (not to learn) the poem.
2. When they (to leave) the beach, the rain already (to start).
3. Arthur (not to know) that we already (to arrive).
4. When I (to come), I (to see) that mother (to cook) dinner.
5. My friend (to study) English before he (to enter) the institute.
6. The car (to go) when I (to look) into the street.
7. He (to take) the decision before I (to come).
8. Nick (return) from office by seven o'clock.
9. We (to get) to the stadium at four o'clock but the game already (to start).
10. She (to come) at six o'clock.
11. I (to think) that my parents already (to return).
12. He (to be sure) that we (not to recognize) him.
13. You (to find) your key which you (to lose) before?
14. Meg (to say) that she (to be) in this city. 1
15. The doctor (to arrive) when we already (to help) him.