Keep a dog upstairs and walk the dog downstairs every day. I was scared to death many times in the corridor. What if I have a heart attack at any time?

Usually dogs bite because they think you are a threat to them. For strangers, they become more aggressive in unfamiliar environments. Generally speaking, big dogs are not as aggressive as small dogs.

Your dog upstairs has been in contact with you many times and should be familiar with you and the environment and will not attack you. Besides, there is no dog owner. As long as the dog doesn't have rabies, nothing should happen. You can get along well without hitting the dog.