what does a German gas chamber look like?
Technically, an automobile could be considered a carbon monoxide gas chamber if the exhaust is directed into the interior.
I don't think gas chambers necessarily look a certain way.
Regardless of arguments about death tolls or whatever else, I asserted that Hitler was responsible for the murder of Jews. This is true. Any person or group of people that place other humans in the circumstances that were encountered by prisoners at the concentration camps is/are responsible for their deaths.
What is your estimate on the number of people that died in the camps, and how did you arrive at that number?
Further, what do you suppose Hitler had in store for the people that he had rounded up from society and shipped to the concentration camps? Do you suppose he planned to release them somewhere? Or, do you suppose he planned to just let them die - regardless of the method?
If he planned to let them die, that - by definition - is a mass extermination plot that was enacted as soon as the society began undergoing forced segregation.