Wow, Mark, these are phrases from the Newbie lessons
?
"auf" is a
preposition, which could mean: at, on, upon, up, onto, in, to and so on.
I don't know, if you have heard about the accusativ and dative. "auf" implies these cases.
"Haben sie noch Lust auf einen kaffee"
"Auf Wiedersehen"
"Wieso haben sie keine Lust auf Kino"
These phrases, which you really use like this in German, are somehow colloquial.
"Haben sie noch Lust auf einen kaffee"
is actually: Haben Sie noch Lust, einen Kaffe trinken zu gehen.
"Auf Wiedersehen"
is actually: "Auf ein Wiedersehen (mit Ihnen)" But "auf Wiedersehen" is really common!
"Wieso haben sie keine Lust auf Kino"
is acutually: Wieso haben Sie keine Lust auf einen Kinobesuch.
Btw, if I have met someone, to whom I talk with "Sie", I wouldn't use "Wieso haben sie keine Lust auf Kino". That doesn't fit somehow. I have to know this person very well to use it
After every "auf" in your sentences follows the accusative, which is not so clear, when you read the lesson-phrases.
I really recommend to take them as set-phraes first. It makes life more easy and I really guess, that a detailled explanation will follow in the beginner or intermediate lessons.