tree in middle of my property and neighbors

[Gp G.]

I have tree in middle of my property and neighbors in the front of building. Also few trees on the back which are kind of in boarder between my property and neighbors property. Whom i have to call from county to make markings to see exactly who owns those trees to cut. I am thinking to put fence also. Can i put fence in the front of building? or only back side fence allowed. please advise