Need to understand the exact requirement based on my specifications

Hi,

My name is Vishal Singhal. I am planning on establishing the ORBI system at my home. My house if a three floor building of 5000 sq feet each. Currently I have a router at the ground floor at one corner with which a wifi range extender (loacted in the center of forst floor) has been connected. However, I am still not able to get signals on the boudry of my home as well as there is very low reception on the second floor. Could you please what shall be the most otimal way to establish my home ORBI system.