That's a really rough translation, so if you're seriously concerned, I would speak to a German intellectual property/copyright lawyer about this to get clarification. But it sounds similar in principle to the law here in the US - if someone is in public, performing a public action, they have no expectation of privacy and you don't need their permission to photograph them. You don't need a model release even if the person is recognizable so long as the work is not being used for commercial purposes. Commercial purposes can be generally understood to mean for the purpose of advertising or endorsing a product or service. So publication in a catalog of photos or exhibition and sale in an art gallery would not require a model release. Putting that photo on a can of Maxwell House coffee, or on a billboard for Joe's Car Repair, would require the release. The German law sounds a little more restrictive, and a little more specific as to the conditions, but not radically different. I'd talk to an expert in local law who knows for sure what the law means and knows case history as to how it has been interpreted. There is probably an organization somewhere in your state, if not a national one, where lawyers who specialize in this kind of law will provide free or inexpensive consultations for artists. Look them up and get advice there. Otherwise, the legal advice you get from an internet chat forum is worth exactly what you paid for it.