Why is he taking so long?
Actually, he's already finished. (Present perfect because he finished in the past, so it is true now that he has finished)
Have you done that?
Yes, I have. (Present perfect, because the question is present perfect, asking if it is true that the job is finished now.)
I really do not know what to do.
Wait! I've had an idea. (Present perfect because Sally had the idea a few seconds ago, but it is important now.)
Have you finished that job for me?
I did it ages ago. (Though the question used present perfect, Sally has used a past tense indicator 'ages ago' so must use a past tense)
I'm so upset
So I see. Have you been crying? (Present perfect continuous is used for something that happened in the past for which you can see evidence for now)
Did you have a good time at the party last night?
Yes, I did. (The question is past tense ['have' is the main verb] so the answer should be past tense as well)