I imagine much like the Romans with Britain, regions that far away are so different and hard to keep relations with in the same manner, say the Mycenaeans towards the German people. I could definitely see relations with the Balkans though. Something that just came to me is if the Germans had relations with these bronze age civilizations, wouldn't it be much more probable that classical Greece and Rome would have had easier access to the region instead of an area isolated from major civilizations at the time? Just food for thought I don't really know