Haha yeah, Im actually half-korean so I might have been able to get away with pretending not to know English but I have a slight American accent when I speak Danish so that's a dead giveaway to them! But yeah, don't get discouraged or annoyed by people switching to English. It sucks, especially when you're like B2 or above but your stuttering may, at times, make you sound like an A1 student. But just struggle through it, the finish line will be that much sweeter.