Goolge Assistant nature sounds only in one speaker.

Hi @SmallAvatar.

Welcome to the Sonos community and thanks for reaching out to us. 

Please see answers below highlighted in red.

1. I have 2 Sonos One in my room, can I use only one for assistant? I mean, can both devices activate mic and the one, which better get results answer me? Yes you can and will only be able to make use of one voice service per sonos system in a given network. The device will determine via voice level to know which voice enabled device are you speaking with. The higher the voice level the closer you are to the voice enabled device.
2. If I say: Google, play nature sounds, the sound comes only from one speaker, but I have a stereo pair. How can I fix it? I would recommend removing and re-adding stereo pair on the Sonos app.
3. Can I adjust voice level of assistant? I want it to answer me quite while I'm asking for the time during night time. As of the moment this is not yet a supported set up, I would suggest lowering the volume level of the device it self on the Sonos App.
4. If I say: Google, Good night, it asks for the alarm first and then set the forest sound. Can I adjust it that Google won't ask for alarm and play forest sounds directly? Can I use speakers to control MiHome devices and other devices related to assistant in the apartment? The alarm feature with voice integration is not yet a supported set up. Please check this guide to know the limitation of the voice integration with Sonos. I would suggest setting up the alarm it self on the Sonos app by following this guide. 

Please let me know if you still have further questions or concerns. We are always here to help.

Thanks,