Microphone usage only possible with bad quality

simple listening to Musik on my H800 Logitech headset works ((Windows Sound is set to "Headphones (H800 Logitech Headset Stereo)" ).

The headset doesn't work in Microsoft Teams or Skype.

My OS is Windows 10.

It seems to only work in two modes:

1) In Ms Teams, when I choose speaker option "Headphones (H800 Logitech Headset Stereo)", I hear my partner very well, but the microhone does not work.

2) If I choose "Headset (H800 Logitech Headset Hands-Free AG Audio)", I hear my partner in very bad quality, and also my partner hears me very bad.

I tried many advices from the Internet but nothing worked:

Un- and reinstall all related drivers

System reboot

re-installed Headset in device manager

Downloaded drivers for the headset (was only available for Windows 7)

Deactivated "Hands Free" Bluetooth option in Device&Printer services (but this just deletes the microphone functionality).

What I expect is that I can use the headset with MS Teams, that I can hear my partner well, that I can use the microphone, and that my partner hears me in good quality.

Spent already a whole day on that and am pretty frustrated.