Demski and Löwner ancestors

Hello to all,

Have received a bit more information from my Aunt to try and narrow down my Omas family. This is what I know so far:-

My Oma was born in Alexandrowsk, Ukraine on Oct 9 1911 to August Jakob Demski and Katharine Elisabeth L�wner, but later raised her family in Oldenburg.
Her parents had come from Danzig, but according to my Aunt were definitely German, not sure if that means they were born in Germany or not. They later settled in L�neburg with their 3 children. It is unknown when and where they both died, it is assumed somewhere in Germany after 1912.
I have been unable to find any trace of either of them so far, can anyone help with ideas of where to look next. Any help would be greatly appreciated.

Tania Taylor