Germany’s brief experiment with a four-day workweek is over, but for many of the businesses that participated, there’s no going back. “I don’t want to work on Fridays anymore. I just don’t,” says Sören Fricke, co-founder of event planner Solidsense. “Friday has actually become the third day of the weekend. You only work if there is no other option.”Solidsense is one of 45 companies that participated in the six-month trial, during which employees worked fewer hours but still received their full p...