Vedlikehold og reparasjoner

I have tomannsbolig in Stavanger. I own the first floor and basement and another owner owns the second floor and loft. The owner who lives on the second floor wants to change the roof, but she dont want to make drenering. The negigbour is saying the roof is important and not drenering. There is leakage from her vaskerom to my room, insurace said there is no sluk and no membrane in her vaseroom so she need to fix it. She is not fixing issues, can we get help to solve this issues.