Past perfect and past perfect progressive

past perfect: used to describe an action finished before another past action. that happened before a specific time in the past.  (both action finished in the past)

Structure: Suject + had+ past participle

https://youtu.be/E7TLPg9ISIA

Past perfect progressive: We used to refer to an ongoing action that ended before another action/event in the past already stared and continued up to another actiion or time in the past 

Structurre: Suject + had been + verb ing 

https://youtu.be/w4VKstoLUrg