Hello,
I'm a learner of English Language and I have a question that has been confusing my mind for all this time. It's about that "The Simple Past Tense vs. The Present Perfect Tense" thing. I already know how to use them when I write something in English (in essays, letters, etc.). I know that I HAVE TO use The Simple Past Tense with a specific time such as "yesterday, in the Middle Ages, 2 minutes ago, seconds ago, etc.". But I just can't decide which one to use when I'm in the middle of a conversation. I visited the US last year and had so many people to talk when I was there.
Every time I try to talk face to face with a person, I get nervous to say something about the past. Actually, saying something about my past really gives me the creeps. I always try to look for a result and that makes me want to use The Present Perfect Tense almost in every sentence about my past because I always find a result

For example, while I was hanging out my friends, my phone rang. I answered. A woman said, "Is Peter there, please?" and blablabla. Then my friends asked, "Who were you talking to?" and I just couldn't decide which tense to use. The Simple Past or The Present Perfect. I mean "I talked to a stranger." or "I've talked to a stranger." So, please, tell me what is the exact difference between The Simple Past or The Present Perfect? Can I use The Present Perfect everywhere without a specific time? Or Is it O.K. to use The Simple Past without a specific time? Because people say "I saw her" or "I've seen her." So what?

It all sounds the same to me.
Warm regards.
Gökhan.