Poor WIFI speed
I have continuously low speed at my WIFI connection (not at LAN-cable, only at WIFI). My internet fiber service provider gives us 1.000 mbps, and by LAN the latest test through the router on site show approx. 900 mbps. However, the big issue is, I can only get approx. 100-110 mbps by WIFI when being just near the router, and 50-80 mbps when being 5 meters from the router, and 20-25 mbps when being on 1st floor just above the router. The router is an Archer C9 dual-band. I have 5 devices using the WIFI, 2 smart phones, 2 tablets and 1 laptop, where I have tried to have these disconnected but without different results at the WIFI-speed. I have tried everything to optimize the WIFI and followed the steps at solution-guides several times . However, nothing seems to be working. What can I do?