We use the Present Perfect Continuous Tense to describe an action that began in the past progress and may also continue in the future.
Subject + have / has + been + verb(ing)...
I have been waiting for the train.
Subject + haven't / hasn't + been + verb(ing)...
I haven't been waiting for the train.
Have / has + subject + been + verb(ing)...?
Has she been watching TV?
Haven't / hasn't + subject + been + verb(ing)...
Haven't they been looking for Victoria?
a. The poor man has been waiting at the corner for an hour.
b. I have been practicing the piano for twenty minutes.
c. How long have you been learning English?
c. How long have you been living in this city?
e. The students have been waiting for the results.
f. Henry has been watching TV since seven o'clock.