I just tried and I can’t reproduce the behaviour you describe. Just to clarify, you clicked on the Kurviger Icon (top, left), go to settings, language, select English and close that popup?
however trivial it might seem - could it be that the documentation page is missing this explanation?
Maybe it would be helpful to add some colorful flags directly in the settings menu - indicating where the languages are? Not everyone knows that “Sprache” is where you change the language, especially if you do not speak one.