Katharina Schüttler as Kasia - are you serious?

I really liked this TV series but this particular actress choice is horribly wrong. This woman is German for God's sake. How come they managed to find a Polish actor to play Piotr (Marcin is great btw) but not a Polish actress to play Kasia? When she speaks "Polish" you can't even understand her. I am really disappointed 'cause they seemed to care about those little details like the brad of vodka in her kitchen. And now this? Like there's not enough Polish immigrants in the UK to choose from...