In Windows 10 or 11 go to Settings and search for Voice. Really looking for the Speech settings.

Choose "+ Add voices" from "Manage voices"
Load the German (Germany) voice package
After loading voice files or files, and from a fresh Mathematica kernel run (not install)
VoiceStyleData[] // Dataset
You should get at least for German (Germany)
Female German Hedda
added to list
The default for VoiceStyleData[]
is Automatic which is what your system supports