Complex sentence: Grafenberg is one of the smallest boroughs in Düsseldorf and its a green area and by the way an expensive place to live (but not as expansive as e.g. Oberkassel).
Split into simpler sentences: Grafenberg is one of the smallest boroughs in Düsseldorf. It is a green area and an expensive place to live (but not as expensive as e.g. Oberkassel).