Perhaps see this Sonos Support link…

https://support.sonos.com/en-us/article/set-up-the-google-assistant-with-a-voice-enabled-sonos-product

Whilst the speaker can be controlled by the Google Assistant, the speaker itself does not support the install of the Assistant. 

Note, on reflection, you maybe out of luck anyway, as the Sonos skill/action required to control Sonos devices with the Google assistant is only available in the countries that are shown here:

https://support.sonos.com/en-us/article/google-assistant-availability-on-sonos

I’m not seeing the czech republic in the list.