It expresses the same actions / events as the past perfect + simple in the a fow on the duration of the actions.
Eg : He had been cooking when a fire broke out.
Conjugate have in the past simple (Had) followed by been and we add ING to the verb.
- Affirmative form
Rule : S + Had + been + ING + C
Eg : - I had been waitting for the bus.
- Sita had been cleaning the yard.
- Interrogative form
Rule : Had + S + been + V + ING + C + ?
Eg : - Had she been dressing in black ?
- Had players been watching their opponents ?
- Negative form
Rule : S + had + not + been + V + ING + C
S + hadn't + been + V + ING + C
Eg : - I had not been listening to him.
- Children hadn't been sleeping together.
- Interronegative form
Rule : Had + S + not + been + V + ING + C + ?
Hadn't + S + been + V + ING + C + ?
Eg : Had we not been advising them ?
Hadn't he been taking are of the shrurbs ?