First of all make sure your curtain is configured properly in Thinka (see KNX) as a window covering. Now just say: "Alexa, close the blinds", "Alexa, turn off the blinds" or "Alexa, open the blinds". You can also open the blinds partly . Then you can just say: “Alexa, set the curtain to 30 percent”. Note that 100% is fully open (most light).