why its so slowly the connection between macbook pro and apple tv?

first of all sorry for my english. I bought a macbook pro this month and an apple tv , everything work fine. But when I try to see my macbook screen trought the apple tv in my smart tv, its imposible. TOO slow, maybe sometimes the image apears , and sudendly not. I was looking in youtube and saw, that people see super fast in the tv. My router is a new one, very expensive. The smart tv is new, everything.

Can anyone tell me whats the problem? why can I see in simultaneus the screen of my macbook pro as fast as I move my mouse in the computer in the smart tv?

sorry if i cant write propertly, thank u very much!