have known OR I know

English as a Second Language English Vocabulary, Grammar and Idioms
1

I have known Sally and Paul since we were at school together.

have known OR I know both are correct…?

2

I have known Sally and Paul since we were at school together.

This is the one to use Ganesh.

3

Thank you so much
when you explain the matter it is like talking to me when I see you photo with a simile