leaking water into our property

For over 2 years I've tried politely and aggressively with letters through Google Translate to have the neighbours fix a pipe leak that flows into our patio from their roof. I can't get any decent use of the patio because it and they don't care, they say they rent, and the owner who is also a neighbour says it's not her. The flow is more frequent now and heavier. Does anyone know if there is a place I can go to for help?

Thank you, but I don't hold out much hope!!