Peter Doerling has listed a couple of genealogical societies and individual researchers who will do research in Schleswig-Holstein
http://www.peter-doerling.de/index.html see: Links für Ahnenforscher
For local history concerning the area of Bordesholm, seeHeimatstube Bordesholm.
For Amt Molfsee, Flintbek, Achterwehr, and Kronshagen an archive exists whose holdings can be checked out at www.molfsee.de. (Archiv). The archive "Eiderkanal" houses records for Bovenau. See www.archivgemeinschaft-gettorf.de