Leakage from above Flat

I stay in Pune. My bedroom ceiling has water leakage since from last 4-5 years. Leakage severity is such a way that we have to collect the water in the buckets. Till now we did 5 times chemical injection process; 3 times at my bedroom ceiling & 2 times from above flat bathrooms corners & floor tiles corners. Each times the water leakage stopped for a year & it reappeared in a year time. Agency who did chemical injection process, has advised to do new waterproofing at above flat by removing bathroom tiles, pipes & reconstruct it. I have been asking above flat owner to rectify his bathroom as per agency advice & he is not cooperating in this matter. Owner is at UK on company assignment since last 3 years & told that he won’t come to India next 2 years. Tenants are staying in his flat. I would like above flat owner to get rectify his bathrooms at his cost as per agency advise i.e to do new waterproofing by removing bathroom tiles, pipes & reconstruct it. How should I handle this leakage issue in legal way? Should I approach Pune District Forum thru a lawyer? Society is not helping in this matter; they ask to solve amicably between both flat owners.