Past Perfect
We used the Past Perfect to express that an event took place at some time in the past before another event (Usually paired with a simple past clause)
I had eaten my dinner before Ahmed arrived. Jane had finished the exam way before the time.
It can be used to express that an event started at some time in the past and continued up to another point of time in the past.
Sammy had owned that car for fifty years before deciding to sell it.
Formulas
Subject + had + past participle + object ( simple past clause)
Subject + had + not (hadn’t) + past participle + object + ( simple past clause)
Had + subject + past participle + object + ( simple past clause )
Hadn’t + subject + past participle + object + ( simple past clause )
Had + subject + not + past participle + object + ( simple past clause )
Information Questions
Q/W + Had + subject + past participle + object + ( simple past clause )
Q/W + Hadn’t + subject + past participle + object + ( simple past clause )
Q/W + Had + subject + not + past participle + object + ( simple past clause )