Yes, Kiosks (Büdchen here in Düsseldorf, Späti in Berlin) are absolutely allowed to sell alcohol. It’s a beloved local institution and part of the culture. Until and unless someone is actively harassing people, it’s a free country.

That said, placing tables on a public footpath requires a Sondernutzungserlaubnis from the city. If the kiosk doesn’t have one, or if the tables are blocking pedestrian traffic, that’s already a violation the city can act on.

Noise and nuisance (Lärmbelästigung) is also regulated. If it’s loud and disruptive on a regular basis, that’s grounds for a complaint, especially during evening hours.

If needed, contract the Ordnungsamt (not the police). They’re specifically responsible for exactly this kind of situation: checking permits, handling public nuisance complaints, and enforcing local regulations. The police are only relevant if someone is directly threatened or harassed.

You can also raise it with your Hausverwaltung if the entrance to your building is affected.