The neighbor upstairs on the opposite side hangs a mirror on the window, which is facing his own home. This means that bad luck is shining on other people's homes. How to solve it?

This approach is harmful to others and not beneficial to oneself. It will eventually lead to a lose-lose outcome and is also morally unacceptable. There will be a backlash phenomenon of "three losses to oneself and seven losses to others".

If the mirror is used to reflect evil spirits, and it is reflected into other people's homes, it is an unethical behavior. If the victim continues to fight back tit for tat, it will inevitably lead to a battle of wits, and eventually both families will suffer at the same time. The best solution is to negotiate a settlement.