This is the best answer, because it gives a Serena little personal information about you and where you met Marie. It also gives you something in common to talk about - school.

Here is a recap of your conversation:
Serena:	"Hi, I'm Serena."
Gisela:	"Hi, my name's Gisela. I'm a friend of Marie's from school."

Now Serena says, "Oh really? Are you a foreign student?"

What should you say?

• Yes I am.

• Yes, I'm learning English.

• Yes, I'm from Germany. I come from Munich which is famous for Oktoberfest.

• I QUIT!