Past simple	Past Perfect
V2	Had + V3

Note:

by/by the time (+ Past simple), before (+ Past Simple/n), after (+ Past Perfect)

Exercises

1) When we (arrive) at the station, the train already (leave).

2) I (be) late because I (miss) the train.

3) I (lose) the ring that he (give) me.

4) Suddenly I (remember) that I (leave) the door open. So, we (have) to go back.

5) By the time we (get) to the theatre, the performance (start).

6) After we (finish) the meals, we (go) home.

7) At the exam I (forget) everything I (learn) before.

8) They (not laugh) because they (hear) the joke before.

9) I (go) to bed by 12.

10) By the time we (come), they (serve) the dinner.