How to fix forced language switch on a bilingual online store?

[tomorrowgolf]

Hi,

my store has two languages, EN and DE. When accessing the store from Austria & Germany, it should by Default display the German version. For all other visitors, the store should be shown in English.

When I access the store now from Austria, it is English. When I want to manually change to German via the language switch button, it forces me to say in English language. I don't know how to fix that...

Thanks!