> 2. all management are German

Questions from someone that knows very little about Germany:

How much of this is the German culture to be educated to a master/PhD level in order to get into management roles? Perhaps that increases the barriers to entry into these levels for immigrants.

How much of this is a language barrier? Immigrants to English-speaking countries have often learned some English before they arrive (often from their schooling) which might put them in a more advantageous position relatively speaking.