I like to think the Count’s first name is Bram
I think it definitely has to be a 'B', owing to Magda's nickname for him 'Bun-Buns'. Bram fits that, and would certainly be in keeping with the Bram Stoker's Dracula references in the show. Additionally, while I'm not able to find any stereotypically Slavic names, consistent with the rest of the family, that start with 'Bram', 'Bran', which is very close, is a quite common prefix.
Another Slavic name that also fits the 'Bun-Buns' nickname is Barnim, and it's connection to a line of Pomeranian Dukes, some of them not nice people, would befit a man of his status.
Of course, we do also have to accept the possibility that his first-name is actually 'Bun-Buns'



























