Main Room: Gauß-Saal: "Großer Sitzungssaal" 3rd Floor (german floor numbering) (left floor, then left when you reach a "bigger" staircase floor until the end)
Break-Out Sessions: Wega: 51 (0/Ground Floor - "end of middle floor/facing the Elbe")
Break-Out Sessions: Atair: 601/602 [6th Floor - ("end of the floor, facing Cuxhaven" (if you face towards the Elbe/are coming from the stairs it is the right floor)