This is a quite common kind of food selling booth. Despite it looks like a pop-up shop, it’s more permanent. In Germany, you can find these food selling booths nearly everywhere. They are selling ice-cream, fish rolls, French fries, bratwurst, döner, waffles and so on: food to eat while walking or simply standing beside the booths. Some of these kinds of food you could find everywhere, others are more regional like this crab selling booth or booths selling fish rolls.
The writing on top of the booth says: “fresh crabs daily” and “unpreserved”. While the writing in the lower right corner says: “not today” 🤣