Neighbors, Nebenkosten, and mistakes (part 1)

I've learned a lot about apartment rental in Germany and about our neighbors in the last few days. And there has been a lot of learning from my own mistakes.

Let me give you a little background for this story.
In Germany, every month renters pay rent for the apartment or house, plus Nebenkosten. Nebenkosten literally means "costs beside", and includes things like water, building maintenance, insurance, garbage pick-up, etc. The landlord determines the amount of Nebenkosten that each tenant should pay every month based on the size or your apartment and how many people are living there. Then, at the end of the year, the landlord compares the actual costs with what you paid in, and you either get money back, break even, or pay extra. 

About two weeks ago, we got the documentation for 2011 Nebenkosten. We owed 388 euros, which seemed like a lot to me. It came with a stack of receipts and bills and cost break-downs and a cover letter stating that costs were high because of a gas leak that had to be repaired. I asked our friend Thorsten to take a look at the letter and clarify what it said. Then I paid the bill. This is dumb foreigner mistake #1.

Then Thursday night, the doorbell rang. The doorbell sounds just like the buzzer from outside the building. Also, there is currently huge Irish flag on the inside of the door and a "Help wanted - no Irish need apply" sign covering our peep hole (in honor of St. Patrick's Day). So I picked up the intercom phone and said "hallo" to no one waiting on the sidewalk outside. This is dumb foreigner mistake #2 because the neighbors were standing outside my door. Claudia and Nordbert from the second floor had come to tell me that the Nebenkosten bills were especially high this year - they owed over 500 and the people below us owed 700 - and there would be a neighbors' meeting at their place on Friday night. They hoped we would come.

This was not my idea of a great way to spend Friday night, but if there was a chance to contest the bill and get the money back, then it was worth trying to follow the conversation.  Since I'd done ok with the chat in front of my door all in German, I felt like I had a shot.
Did I really? How many other dumb foreigner mistakes would I make? Read on to find out in part 2...