Past Tenses (Perfekt, Präteritum, Plusquamperfekt)
What is the Plusquamperfekt and when do I use it?
The Plusquamperfekt (past perfect) describes an action that happened before another past action. It's the "past of the past."
Formation: Präteritum of haben or sein + Partizip II.
Example
Nachdem ich gegessen hatte, ging ich ins Bett. (I had eaten before I went to bed.)
Als er ankam, war ich schon gegangen. (I had already left before he arrived.)