UR12 howto set device to 16bit operation?

Is it possible, and if, how can I
Set the UR12 in 16bit operation mode,
I only see "2 channel 24bit, 44100 Hz (studio Quality)
If it isn’t possible with a UR12, can someone recommend another sound-device?

From your description it looks like you are alking about the settings in Win10. And if that is the case, just go to the sound settings in the control panel (settings->sound->sound in control panel on the right side of the page), select ur12, advanced tab, then choose the bit depth and sampling frequency in the drop down menu.

Yes Win10
If that’s is the way I am sure it is not supported.
I only have the option “2 channel 24bit, 44100 Hz (studio Quality)” there

Ok, then something else is amiss, I am not with my music computer atm, so I’ll have to get back to you. But it could be a service that has taken control of your sound card, so check that you don’t have anything running on your computer (like a DAW)