1. Barking: The mediator recommends that neighbor Andrew provide the dog with appropriate training (e.g., consultation with a veterinarian or a canine behaviorist) and take steps to reduce barking (more exercise, mental stimulation). If the barking does not subside, I suggest a visit to the municipal inspectorate for neighborhood peace, which may order measures.
2. Muzzle in common areas: I recommend that neighbor Andrew consistently place a muzzle on the dog in the elevator and hallways of the building, as required by the house rules of most buildings and the Animal Protection Act. A German Shepherd is a large dog, regardless of friendliness.
3. Agreement: I propose that neighbors Michael and Andrew conclude an agreement: neighbor Andrew limits barking (e.g., by providing a quiet corner at night), and initiator Michael tolerates normal daytime sounds. If the agreement does not work, I suggest a written warning to the building manager.
Concluding note: Initiator Michael noted that "a large dog does not belong in a block of flats," but this is not essential. The problem is not the size, but that the dog causes noise in the elevator. I advise neighbor Andrew to provide the dog with appropriate training and a muzzle to prevent disturbing the neighbors.