Dampness caused by constant water leaking by neighbors

My 1st floor unit in a 3 storey building in Uttam Nagar, Delhi getting ruined by constant dampness caused by water leaking by households on ground and 2nd floor. Three water tanks installed on rooftop, one each for each household living on three floors. Households on ground and 2nd floor refills their water tank many times during the day which causes water to overflow from their water tanks. Water overflow from tanks travel down the shaft from top to the bottom. My bathroom and the room adjacent to it close to the shaft gets constant exposure to water leaking, hence both the bathroom and the room adjacent to it have developed dampness. A part of ceiling in bathroom fell apart and came down heavily on the floor one day in the middle of the night. Luckily no one got injured. Rest of the bathroom ceiling and walls also slowly falling apart. The top layer of walls have also started falling. What remedies are available and under what sections & provisions of what Acts. Please advice.