past simple or past perfect:1. They (lock) the gates before I

Past simple or past perfect:
1. They (lock) the gates before I (get) there
2. By the time I (arrive), the party (finish)
3. When she (ring) the office this morning, Jim (already go out)
4. Before we (take) Tim this the theatre, he (never see) a stage play before
5. I (just clean) the carpet when the dog (come) in and (shake) himself
6. They (eat) everything by the time I (arrive) at the party
7. The car (go) when I (look) into the street
8. I (not finish) getting off the train when it suddenly (start) moving
9. We (not finish) cleaning the machine, but we (decide) to stop work
10.They (decide) to get married last month, although they (know) each other for only six weeks

пожалуйста, помогите! но только если точно понимаете!!