In Germany you see things like a single person having to do all jobs at once at a Pizza Hut or only three people working at the same time in a supermarket. A lot of customer-facing businesses are insanely understaffed. If your employer doesn't hire enough coworkers for whatever reason, your life will be miserable.

Isnt there a maximum average hours of work around 40 a week in Germany?

Yes, with a few exceptions it's restricted to a maximum of 8 hours a day on average (and 10 hours max), with 5 days a week.

However, how much stress you can be exposed to in those 8 hours isn't mandated. You can run many businesses understaffed with fairly little impact if you are willing to regularly replace employees suffering from burnout [1]

1: https://en.wikipedia.org/wiki/Occupational_burnout

Sounds about right. EU Working Time Directive is something like 40 or 48, but my German isn’t good enough to read German law.