When should we use the past perfect continuous tense?

When we need

It is ues when we talk about sth started in the past and continued up until another time in the past.

E.g . He 's out of breath. He has been running

. You can  say that sth had been happening for a period of time before sth else happened 

we ues the present perfect continuous when we talk about how long an action's been happening ,and it's used with "for" eg: I have been teaching for ten years / He has been playing football for five years

Actually, it is used when anyone talks about an action happened and took time in the past without mentioning the exact time like " I have been doing this task for hours." this took time in the past and it may have an obvious effect now. Or to speak about an action that was going on since a certain time till now like " I have been sending letters to my friends since we finished college." I hope this could really help !! 

when the action began in the past; it's taking place right now and it will continue for an indefinitive period in the time

To reflect the event began in the past but did not end up before the occurrence of another event in the past

It expresses something lasted for a period of time in the past and finished before something else happened.

She had been writing all day when I arrived.

It means she took all day writing and I arrived after she finished.

past perfect continuous used to show some thing started at the past and stayed for time then finished at the past too

Past Perfect Continuous is used to show that something started in the past and continued up until another time in the past. The both duration in the past only.

And in the present perfect continuous the action continued up to now or in the present time

Rarely. When we describe events un the past, which had beginng, contination and ending

Usually we use the continuous tense when we want to refer to an action that was happening during a specific period of time wheather this tense was present or past .

In our case we use to refer to two events in the past but one of them was happening and continued for a while in a period of time in the past.

I had a teacher from England when I was in collage she was called Mrs Margret ,I was using tenses and used to ask her when I should use this tense or the other and which one I shoud use first, she replied me first and followed, you Egyptians want to be British than the British themselves and of course things don,t go on that way .

thanks a lot.