Two: choose to stay away from the kitchen and restaurant (because you have to cook and eat)
Third: the bathroom should be located at the edge or corner of the house (because drainage and exhaust are relatively easy and reasonable)!
Four: the bathroom window should be set in the east and west directions (because there is plenty of sunshine on both sides, it can be lit, and there will be no smell because of the north-south wind)
Of course, if your building has a large use area, I suggest you set one in your bedroom, because sometimes it is cold in winter and it is closer to your mind to sleep until midnight at night. If it's small, put it near the bedroom!