Dear Yves Depardieu,
Thank you for posting your inquiry on History Hub!
We searched the National Archives Catalog within the National Archives Collection of Foreign Records Seized (Record Group 242) for “Heringen.” The search results can be found here.
Also, you might want to look into records of the Reichsamt für Bodenforschung since they may contain information of interest to you.
In addition, we would suggest contacting the German Bundesarchiv as they may have relevant records in their holdings. They may be contacted at: https://www.bundesarchiv.de/EN/Navigation/Meta/Kontakt/kontakt.html
We hope this information is helpful. Best of luck with your research!