Remember that the present perfect is the present tense, not the past tense. It tells us that the action started earlier and it has just ended or it is still going on.
We use the present perfect in the following cases.
1. How long
We use the present perfect in questions with how long and answers to these question. We answer with the words for or since.
"For" means a period, for example, for several days, for five years, for two months etc.
"Since" means starting from some date, for example, since Monday, since 1999, since school days etc.
— How long have you lived in Toronto?
— I've lived in Toronto for three years.
— How long have you known Isabel?
— I've known her since 2015.
2. Action has just happened
Something has happened recently and it is important for the present moment.
He has missed the flight.
→ That means he has just missed it, now he must buy a new ticket, change his plans and so on.
She has passed the interview.
→ She has done well recently and now she'll get the job.
Remember these signal words that tell us to use the present perfect:
just — a short time before
already — before we expected
yet — like "already" but for negatives and questions
He has just called the police.
We have already had breakfast.
Have you started the exercise yet?
My friends haven't arrived yet.
3. Never, once, twice...
Something has already happened several times so far and may happen again.
He has visited Kiev four times.
→ We mean that he is still alive and he can go to Kiev again.
She has drunk two cups of tea today.
→ We mean that the day is not over yet and she can have a few more cups of tea.
When we talk about an experience (have ever done something / been somewhere), we also use the present perfect.
Remember the words:
ever for questions, means "one or more times"
never for answers, means not even one time.
— Have you ever been to Australia?
— No, I've never been there.
— Has he ever ridden a horse?
— Yes, he has ridden a horse once.