When do we use Present Perfect Continuous?
For duration and ongoing activities
Present Perfect Continuous focuses on HOW LONG an activity has been going on, or on a recent activity whose effects are visible now. The activity started in the past and is still ongoing (or just stopped).
The activity started in the past and is still continuing now.
Lily has been training for three months.
"for" + duration
I have been studying since 9 am.
"since" + starting point
How long have you been waiting?
"how long" question
The activity has just stopped but its effects are visible now.
You look tired. Have you been running?
visible result = tired
Her eyes are red. She has been crying.
visible result = red eyes
The ground is wet. It has been raining.
visible result = wet ground
Focus is on the PROCESS and DURATION, not the completion. "I have been reading." (still reading or just stopped) vs "I have read the book." (finished = result)