Only once we get a glimpse of Harald, the teacher, who lives alone on the top floor.
We see Frau Hinz passing him the daily newspaper he has a subscription for. (see episode 5)
So we have proof of him being a tenant in the house.
Harald is a shy, reserved person living a very secluded life.
He is not interested in socializing with the other tenants, does not enjoy gossiping and refrains from sharing the events or non-events in his life with others.