Home setup

Hi everyone, sorry but I'm having issues with the WiFi service in my house and I'm certain my tech is either super outdated or I haven't got it all setup properly and hoping for some solutions as home wifi networking is a blind spot for me and I don't understand it all.

I have Verizon as my ISP, I use the Quantum Gateway Router they provided. This is on the first floor. In the basement of my house is a Netgear EX7000 Nighthawk Range Extender. 

The problem I have is that my house is long and narrow. The Verizon Gateway router is near the back of the main floor, the Nighthawk is closer to the middle of the house in the basement. I would "think" this would give me excellent coverage throughout the entire house (about 1200 square feet on each floor) but the front of the my house and my basement still get spotty coverage and the wifi checks in and out all the time in the basement (noticeably most when I'm on conference calls or playing my PS4). 

My mother-in-law recently purchased the AX11000 Wifi 6 router and she says it covers her entire farmhouse so that's intriguing. Perhaps my EX7000 is outdated but I don't want to drop $$$ on a new router or a new extender or whatever if that isn't the proper solution. Any help would be appreciated from the community.