One's "own four walls" is a very important subject to Germans. That is why most homes are very neat and tidy. Even stairways and common rooms are treated carefully and with respect. The strict separation of waste also reflects a sense for cleanliness inside and outside of German homes.
Living as they tend to do in such tidy and cosy homes, Germans mostly keep to themselves. Usually, one does not know the people next door. At the same time, one tries hard not to disturb the neighbours. There is even a law that stipulates that everyone must stop making noise after 10 pm. After that time it is strictly forbidden to play loud music or make other disturbing noise in your flat.
Further information on this can be found in the house rules, which should be attached to your tenancy agreement. Click on this link to read an example