Help with ATT Gigapower Wireless

7 years after moving into a brand new neighborhood ATT finally laid the fiber to bring high speed internet in. My question is to how to wirelessly transit the highest speed possible. When I hardwire into the modem I'm getting 900+ Mbps but the ATT wireless router built in only transmits at around 50 Mbps. After some aimless searching online it seemed as though I needed a better router. Given my need for instant gratification I drove up to Walmart and got the linksys 1900ac for a little over $200 without doing any research. I think I've disabled the ATT wireless and have the linksys as the only wireless transmission but I'm only getting about 80 Mbps now. I'm sure I'm on the 5 and not the 2.4 broadcast but other than that I'm stumped. I've already decided I was going to have to hard wire the tv for streaming but is there anything I can to improve the signal for my other devices? The house is only 1 story and about 2000 SF so I'm not more than about 30' from the router. TIA