How much will I learn in Germany?

I'm traveling to Germany for exactly 4 weeks, and my question is, how much German can I/will I learn. I know some very basic words but that's about all I know.

Please don't answer that it just depends on the person. I'm a relatively fast learner and maintain good grades in difficult classes.

I will be in Germany during the summer with my girlfriend, and staying with her family. I'm really eager to learn, and aspire to be fluent. I already know I have a short amount of time, but how much can a typical person learn in 28 days of pure immersion?

Any personal experiences would be great!

Oh and by the way, is there any way I can learn my German faster before I go? I'm studying off of an iPhone app currently.

Don't go

I use the instant immersion german program comes with ipod tools n stuff works pretty good way cheaper than rosetta stone cost me like 30 bucks

I have a German girl friend. So at first it was hard for me. The best way to learn is to listen when people speak. To be around real situations.

Almost everyone under 40 speaks English in Germany. Make sure you let them know that you want to be spoken to in German or they'll speak English and you won't learn much. When you go some place don't be shy to try to speak German, explain with hands and feet if necessary.

Since you seem to be a fast learner and will stay with your girlfriend's family you will learn quite a bit of German, however, to be somewhat fluent you need to live there for a minimum of 2 years, and that's a fact.

You could learn quite a lot with total immersion over the 4 weeks. You'll be exhausted for the few couple of days, but you'll get used to it.

Start with basic phrases, and go from there.