Another idea would be, to either announce it via small ads in the Anzeiger or at the local coop and Migros stores messageboards.
Try to hold a 'car boot' sale from your home.
Set a fixed day and and a time,say Saturday afternoon from 1 to 6 pm
HAUSRÄUMUNGSVERKAUF , alles muss weg

followed by the address.
You'd be surprised at how many ppl turn up to these!
Add specific info on the ad, such as the address and your cell phone.
Maybe it's possible to set up a makeshift stall in front of the house you live, or you could empty your cellar compartment for the afternoon and put everything you want to sell in there ( in case you don't want strangers in your flat)