Picture Perfect Dialog: Put the lines in order and see the picture.

Use the clues to arrange this dialog in the correct order. First, read all the lines; then try to arrange them in order from 1 to 18. There are hints below...if you need them. Try to think logically. Here is the dialog:
Hi, Trudi.
Hi, Hans.
Who is that?
The boy? That's Karl.
WHAT'S his name?
Karl Schmidt.
And the girl. What's her name?
Her name is Beate. That's Karls sister.
Oh. Her name is Beate?
Yes.
Nice. How old is Karl?
He is 15
15? I'm 15 too.
Yes. But Beate is only 13.
Hmm. She is too young for me. See ya.
See ya.