Hi Underjakk,
Being from the Netherlands I have tried to make a Beerenburg and I think I can at least help you out to get started.
First of all; Beerenburg was originally made by fisherman who bought a mixture of herbs in Amsterdam from a man named Hendrik Beerenburg, they macerated the herbs in Brandy or Genevre while fishing. Nowadays there is a multitude of different spirits that all differ slightly, both named Beerenburg and Berenburg.
The Braumarkt reference you give is for a mixture made by the company Jacob Hooy, they claim to provide the original herbal mixture. Most pe