Questions about present perfect

From my understanding, one of the main difference between past simple and present perfect is that

present perfect describes something that is done before, and is still affecting now, whereas past simple describes something that is finished in the past.

So, I have two questions.

I watched a film a few days ago, And an actor is confused that he might have infected his girlfriend, and he's told that "If you don't have it, there is no way you've given it to her." by his friend.

and I don't understand why present perfect is being used in this case. Will it be wrong to say "if you don't have it, there is no way you gave it to her."

And the second question is, why is 'done' used more like past simple? As I mentioned, present perfect describes something that's still affecting now, But I think 'done' is saying pretty clear that something is completely finished, and is not affecting now anymore. (as in 'I'm done with it!')

I'm not a native speaker, so my english might be a little strange. sorry for that. And I will be glad if you correct me.