Solved. After research in the code, it was clear Shelly DUO RGBW is supported.
Problem is that openHAB 3.0.1 does not include the latest Shelly binding.
After update to openHAB 3.1.0 M2 (milestone 2, pre-release) it works.
Connect via Terminal to openHAB: "sudo openhabian-config" you can update it under menu "40"
maybe that helps someone who has same issue