BK1 speaks this hybrid language, and further hybridises it by adding English words and expressions.
This happens when BK2 utters the words "Buch" and "Schoss", and BK1 reprises them in their conversation which is usually in Arabic. Now why does BK1 not translate the German words into Arabic or French? Is it because of the limitations of her vocabulary in these two languages? Is it because she is used to hybridising Arabic with French and/or English, so adding German to the equation is natural to her?
Will the girls ever speak Arabic properly, with minimal mixing? Only time will tell, and these are early days.