Purpose: When you have two actions in the past, the earlier one takes past perfect; the later one takes past simple.
- Before I moved to China to teach English, I had worked at several schools in Canada.
- The staff kicked the customer out of the store because he had behaved rudely.
- The boss fired him because the boss had asked him to improve his sales performance and he couldn’t.
- He was fired because he had been asked to improve his sales performance and he couldn’t.
Note these differences between past perfect continuous and past perfect:
These two forms are often confused because the auxiliary (helper) verbs - had been – are the same. But one is active voice and the other is passive voice:
Past perfect, passive voice: had been asked
Past perfect continuous, active voice: had been asking
He had been asked for his ID at the door, but it later turned out to be fake.
He had been asking for you, but then he left before you could get here.