Slow wifi

Some tips for improving WiFi performance;

http://corporate.comcast.com/comcast-voices/10-ways-you-might-be-killing-your-home-wi-fi-signal 

https://www.xfinity.com/support/articles/improve-your-wireless-home-network 

There are other options. Google for WiFi repeaters / range extenders, WiFi mesh systems / pods. Good luck !

https://www.cnet.com/how-to/your-router-isnt-as-fast-as-you-think-it-is-heres-why/ 

https://www.cnet.com/how-to/home-networking-explained-part-2-optimizing-your-wi-fi-network/ 

http://www.metageek.com/training/resources/design-dual-band-wifi.html