@CorradoFiori
Hello, the country code of the router should be fixed; what is the country version of this Archer AX6000? It is printed on the back panel of the actual router, next to the router.
You can change some wireless settings to improve the wifi coverage area, like wireless channel, channel width and transmit power.
For 2.4GHz, you can use channel 1, 6 and 11, channel width as 40MHz; for 5GHz, use channel 36, 40 or 44 and channel width 80Mhz. And please set transmit power to high.
What is more, you can adjust the location of the router and the position of antennas to improve the wireless performance. Or you can add some network expansion devices to boost wifi signal, like range extender, powerline adapters.
May it help.