When do we use the present perfect:
for something that started in the past and continues in the present:
They've been married for nearly fifty years.
She has lived in Liverpool all her life.
He has written three books and he is working on another one.
We often use the adverb ever to talk about experience up to the present:
My last birthday was the worst day I have ever had.
and we use never for the negative form:
Have you ever met George?
Yes, but I've never met his wife.