"Checked on site Sept. 15th, 2023. Windows are boarded up. No sign of active business."
The place has gone or never existed. A user of Organic Maps application has reported that the POI was visible on the map (see snapshot date below), but was not found on the ground.
OSM snapshot date: 2023-08-14T02:00:17Z
POI name: American Diner
POI types: cuisine-burger amenity-fast_food
#organicmaps android

"Nicht nur Laden, sondern auch Kräutergarten zur Besichtigung."
OSM snapshot date: 2024-08-10T16:22:45Z
POI name: Kräuterpark Altenau
POI types: shop-tea
#organicmaps android

Unable to answer "Is this still here?" – Deicke (Car Repair Shop) – way/180173857 via StreetComplete 58.2:

Ebenfalls Auto-Point Altenau

"Dies ist kein normales Restaurant. Gekocht wird nur für Gruppen und nach Voranmeldung."
OSM snapshot date: 2024-08-10T16:22:45Z
POI name: Bürgerhaus
POI types: amenity-restaurant
#organicmaps android

Unable to answer "Is the water potable here?" – Ziehbrunnen (Water Well) – node/1457566195 via StreetComplete 58.2:

Der Brunnen ist vergittert, nicht öffentlich zugänglich

Unable to answer "Is this still here?" – Mietflitzer (Car Rental) – node/6220985000 via StreetComplete 58.2:

CGC Immobilien

"Bitte Kategorie Restaurant hinzufügen"
OSM snapshot date: 2024-08-10T16:22:45Z
POI name: Fleischerei Baumann
POI types: shop-butcher internet_access-wlan
#organicmaps android

Ferienwohnung Haus Ariadne ist in Nr. 5, nicht Nr. 7

via StreetComplete 58.2

Unable to answer "Is this still here?" – Dr. Hoppe (Dentist) – node/4403776989 via StreetComplete 58.2:

Heine & Meins, Steuerberater

Unable to answer "Is this still here?" – Dr. Hoppe (Dentist) – node/4403776989 via StreetComplete 58.2:

Dentalmedizin Hamburg