“Have you seen the new Mission Impossible film?”

Rule 1:

Use the present perfect to talk about a general experience in the past. Use the past simple to talk about a specific moment in the past.

“Have you seen the new Mission Impossible film?”
“Yes, I have.”
“When did you see it?”
“I saw it last week.”

Use the present perfect for “unspecified” time:

I’ve seen the new Mission Impossible film.

Use the past simple for “specified” time:

I saw the new Mission Impossible film last week.

Rule 2:

Use the present perfect to talk about an action that started in the past and continues to the present. Use the past simple to talk about an action that started and finished in the past.

Use the present perfect for “unfinished” time:

“I’ve lived in Brazil for three years.” (and I live in Brazil now)

Use the past simple for “finished” time:

“I lived in Brazil for three years.” (and I don’t live in Brazil now)