In America you have Craigslist. In Germany, Americans have Heidelberg/Bamburg/Ramstein/Mannheim/Stuttgart Yardsales.
This is the place to buy other people’s crap and get rid of your own. We’ve purchased everything from a treadmill to my car on yardsales.com. When we needed to get rid of a box spring we had over 12 people email us within an hour of posting. The boxspring was gone less than a couple of hours later. People I work with have talked about being addicted to searching for the most random stuff on the website. It’s a great place to find a deal or to waste some time.