Working on Sundays is generally prohibited in Germany in accordance with Section 9 (1) of the Working Hours Act (ArbZG). The employment contract states exactly how long your working week is. As a rule, this is specified as Monday to Saturday and the employee may not be required to work on Sundays.
There are only a few exceptions to this, such as hospitals or catering businesses, whose activities typically also have to be carried out on a Sunday. Outside of these activities, working on Sundays requires a statutory order or approval from a supervisory authority.