Harrassment by neighbour

We are based in Dehradun and have a 2 acre orchard which is an acquired land since past 60 years, right infront of our house. The neighbour next to our orchard also have acquired the adjacent piece of land and has built a hostel there. We have built our independent wall as a boundary as this fellow has been trying to trouble us ever since my father died and my mother n sister are alone. Firstly he built a sewage opening of his hostel's bathroom into our orchard and even after requesting him several times to close it, he did not paid any attention to it. Due to this we had to construct a wall against his to close the opening. Now he has started throwing garbage in the orchard from his terrace and also have placed his split air conditioner fan unit on our side. After so many attempts to resolve the issue amicably, he doesn't seem to co-operate and has been harrassing us in some way or the other. Please advise if we can file a FIR against him and if there is any provision in law where we get some rights as citizens against such issues. Please help as to what can we do to secure our property which is unregistered as of now (as no registry is opened as of now as it comes under cantonment board). We hv been paying property tax and water tax all throughout. We will be highly obliged.