[Ger-Poland-Volhynia] Research in other areas of Germany

[gswilson19 at aol.com]

Hello,
I tried posting this on the Stolp list and did not get any response.  I know a lot of people on 
this list are very knowledgeable and hope someone can help me.  My Lemke family was from Rettkewitz
and later moved to an unknown place as of yet. I have very little info on the family.
  
erman Lemke was married to Pauline Jantz abt 1874.  Pauline is the daughter of Carl Jantz and 
Henriette Wilhelmine Pelzer.  Herman and Pauline have a son Max born 1879 (in Rettkewitz?).  At 
least two daughters, one who is Emily.
In Oct of 1898 Max Lemke was a "higher noncommissioned officer in the 2nd Guard regiment in Berlin.
By December of 1899 he is a Sergeant.
Emily was married by 1899 and living in a suburb of Berlin.  Husbands name is unknown. 
I am familiar with most of the resources available in other areas but don't know how to research 
the family further in Berlin? Can anyone suggest how I can proceed with such limited information?
hank you,
Gail Wilson