How to get 2GB with XB8?

Hi ,

Xfinity has upgraded my modem to the XB8 so that I can get 2Gbps and while the bandwidth coming to the modem is 2Gbps (running Xfinity test in the app) , it drops when connecting on the Wifi or even when connecting another router (TP link EX75pro) from any device (laptop or phone). I am only getting about 600mbs. Any idea why or how to solve this?