Leakage from above flat

Dear Sirs I love in Mira rd , there is a leakage from the flat above mine due to which my hall ceiling has been damaged, now also in the passage area between hall and bedroom there is a leakage from the ceiling and continuously drop of water is falling due to which i have place a bucket there. I have i formed society verbally but they are always uninterested in any issues, alai i firmed owner of above flat and he says leakage is not form his flat, due to lockdown I am unable to get any plumber to check the leakage. Can you please advise when i arrange a plumber who is responsible to pay for the work to be done and secondly what about the damage that it has caused my ceiling, i am also afraid of water enters the light socket it can be dangerous, can you please advise as to what are the options i can pursue and who has to bear the costs. Thanks