Why many German girls are introvert,reserved,arrogant and unfriendly especially towards foreigners?
"Many"? How many is "many"? How many have you met?
That was not my experience when I visited Germany. They were very friendly.
From experience (I have a German step-mother) a lot of Germans (not confined to girls) appear arrogant (many!), reserved (Europeans tend to mind their own business unless asked/approached) and therefore unfriendly. Introverted - not so much.
Been There, Done That.
If you're black, that's the reason.
are you sure? here in europe they are perceived as very ''open-mind'' girls.
because you address them in English
Maybe you keep trying to meet the same type.
Not just girls. That tends to be centuries old proper German culture.