Extermination (Death) Camps
They were used for mass murder by the Nazis.
Concentration camps were created for the purpose of exterminating "undesirable" persons- primarily Jews. Among the means used to kill a lot of people quickly were "gas chambers". These were airtight rooms that could be filled with poison gas, causing the death of everyone in the rooms.
The Nazis did not plan to murder all prisoners in camps built before the Holocaust
You have that backwards. The Nazis killed the Jews by the millions during the holocaust. Few civilian Jews killed the Nazis. During the Polish uprising of Jews in Warsaw, the civilian Jews armed themselves and fought against the German soldiers trying to murder them.
The Nazis did not plan to murder all prisoners in camps built before the Holocaust
European Jews
Birkenau was built after the Nazis knew more about the mechanics of the murdering process. It was seen as the industrialisation of murder.
The Nazis Strike was created in 1943.
Colossus
The Nazis Strike was created in 1943.
The Holocaust .
The Nazi party was non-religious, so yes the Nazis did murder on Sundays.