IS THIS LEGAL?

My neighbor built this structure on our duel garage. Previously both garages looked the same. He flattened out the roof and built this Gazebo. His contractor filed paperwork with the building dept and when a complaint was made an inspector was called who seems to have signed off on this as well. I don?t know the details since this is my mothers house and I was away when all this happened about two years ago. However, the following things seem strange to me and I would like to understand how this could have been approved. 1\. The roof extends onto my property line. I cannot obviously build the same structure on my garage without smashing into his roof. 2\. there is no pitch between my roof and the wall he built so water does not drain off and instead pools there. 3\. There is water damage to my trim and probably to the interior under my roof as well. I believe this is due to there not being a pitch. 4\. My entire garage seems to be listing slightly down on the left side. I assume this is because the weight on his side is affecting me. Please, I can use advice on how to proceed. I tried talking to him since I do not want to call the building dept on my neighbor and he said he did everything right and got approval so he is not obliged to fix or change anything.