Talking about the 185 days rule one has to distinguish between renewing a license and obtaining a license for the first time.
If you live in Germany for > 185 days (the date of your "Anmeldung") and you make your driving license for the first time (i.e. pass the examn) in Bulgaria, your license will not be valid in Germany. I also won't be valid if you make it in any other EU country, by the way. The rules have become quite strict to stop what was called "Driver's License Tourism" where formerly German people who lost their license for whatever reason just made a new one from sratch in the Czech republic for example. (There used to be agencies who arranged everything for you.)
I know of cases where people who's background is in another EU country just didn't want to make their driving license in Germany because the cost is about 5 times what it costs in Bulgaria, then went to the German Führerscheinstelle and wanted to exchange their license into a German one. They came back with a huge sticker on their bulgarian license saying "Not valid in Germany." But again, this is about when you were granted the license initially, not about renewal.
Check your license. On the front it says when the license document got issued, on the back it will list when you were granted each class.