Hello, of course, it's a leaking toilet or a blocked floor drain pipe. The sewer pipe in the toilet is blocked, blocked. There must be poor drainage. Is it your problem? !
Call a toilet pipe to clean the master's room. I think it's blocked? Let the master who dredges the pipe come to the door to solve the problem, negotiate with the property in advance, and let all users who use this sewer pipe share the dredging cost.
At the same time, let the property tell them not to throw garbage, kitchen waste and toilet paper into the toilet.