Dysfunctional voice control dictation

I would like to use voice control dictation for dictation in German. In English, it works perfectly. When I switch on German my relatively new MacBook Pro M1 starts behaving very strangely. The floating Voice control microphone window disappears and reappears again constantly and does not react to clicking. All programs get very slow and the spinning Colorwheel appears regularly. As soon as I turn off voice control or switch back to English everything behaves normal again. I don’t find any information online about this problem so maybe somebody here knows what is going on and how to solve it. I definitely would appreciate that!
Have a nice summer and greetings, Per