About where the names are from:
There are no official German names for gminas in Poland, however their Polish names just consist of the word "gmina" followed by the name of their administrative city. What i did is combine these city names that are already present on the city's respective node ("admin_centre" of the gmina relation) together with "Gemeinde" (German word for "Gmina").
In addition to that, i checked most of the names with http://gov.genealogy.net that visualizes various historical sources regarding city names. In case of https://www.openstreetmap.org/relation/2613078 i used the "name:de" tag from https://www.openstreetmap.org/node/31580922, which is "Groß Born". It also matches with this entry on genealogy.net: http://gov.genealogy.net/item/show/BOROR2JO83GN
("Bahnhof" is just the German word for railway station, followed up by the city name "Groß Born")

This name is also present on the German Wikipedia page of Borne Sulinowo, which is probably the reason it was added to OSM.

The issue of the usage of "name:de" and "old_name:de" has been discussed multiple times by the German community with most people agreeing to keep using "name:de" for names that were not part of a political renaming campaign (like changed names introduced during WW2). These should instead be tagged with old_name:de:-1945 or similar. I also checked most of the names for that, but i did not find any.

Here are some examples of representative opinions on the topic:
https://lists.openstreetmap.org/pipermail/talk/2014-March/069416.html
https://lists.openstreetmap.org/pipermail/talk/2014-March/069422.html

Thanks for letting me know about adding the native name in addition to any multilingual name, i will do that in case of any further editing like this.