Turning phone down without opening siri

Hi,

This morning after I woke up my Iphone 11 pro max decided to not respond at the touch of my fingers.

I tried to turn my phone down but everytime I did this, Siri opened up and I could not finish. I tried to restart my phone completly but my phone did not react to that too.

How is it possible that it decided not to work when I had not any problem yesterday?