From material posted online I think you are looking for a family tree in the wrong part of the country! You likely want BALDENBURG, in Westpreussen (West Prussia) as the passport you mention clearly shows that the father was from Gellin, Ostpreussen (East Prussia) although it might be Gellin in Pomerania. There are not many records available on microfilm for these villages, but if you do a google search of Nimz, NIMTZ and Gellin, you will find a link on GEDBAS that shows some branches of the tree, although from their data no direct linkage is shown, but I don't think posting on this board will connect you to anyone researching that family. Just my opinion of course, so you might want to check out this lead. Good luck with your research.