I can't speak to Germany, but in some places it's not legal to have you work over public holidays as the company would have to pay you extra plus giving you leave to make up for it. If they don't want to do that, you aren't allowed to work.

Everywhere I've lived and worked (only two countries, tbf), the idea of working on a holiday weekend is just ... not considered, outside of being on call and getting paid extra for it or similar.