Thanks for explanationOriginally Posted by DandelionThe past perfect expresses an activity that was completed before another activity or time in the past.
Everyone had spoken by the time I arrived.
Everyone had spoken by 10 a.m.
If either before or after is used in the sentence, the past perfect is not necessary because the time relationship is already clear. The two sentences below have the same meaning and both are grammatically correct.
Sam left before Ann got there.
Sam had left before Ann got there.
Hope this helps.