past perfect – Bildung und praktische Anwendung
The past perfect is used in English whenever an action in the past had begun and is completed, before another action begins.
The past perfect if not used by itself, but mostly in connection witht the simple past
The the past perfect is formed by help of the auxiliary had in connection with the past participle.
When negation simply add not to the auxiliary had.
The short form is accordingly hadn't
The question shifts the auxiliary to the front of the sentence: (inversion)