Yes it is. Shepherds are working dogs they need a lot of exercise not just physical but mental as well. My point was that there are legal definitions for the complaints in the landlord’s letter and it is possible that the dog’s behavior did not meet them.
Yes - that was my point as well. German Shepards are big dogs with a lot of energy. Who is exercising the dog? Is the dog getting out to run? How often? It’s not natural for the poor dog to be shut up in a small apartment.