Sort:  

Although I do not understand what you say
But I would like to learn some words to fight you
I'm kidding I'll learn because I love German

As a joke, I had said:

"Yes, I'll start by answering you in German; -)
The grammar is so difficult in German."

Ah good so this is the first lesson?

Ja, das ist die erste Übung.

Nun, danke für diese Lektion
Wir sehen uns andere Lektionen