Past continuous is used when you did something in the past but this action is still continuing.
Example: I was walking;
Presente perfect is used when you did something in the past, but there is not a specific time.
Example: I have read a book (I don't use a specific time here)
Present perfect continuous is used when you did something in the past (there is not a specific time as well) and this action affects the current time.
Example: I have been waiting for a while.