What should I do if the upstairs leaks and the downstairs property is not handled?

If the water leaks from upstairs to downstairs, first make sure that the water leakage is the responsibility of the upstairs, and then collect evidence. The general solutions are: first, communicate with the neighbors upstairs and ask them to repair and compensate for the losses caused. Second, if communication can't be solved, you can find a property or street community to mediate.