Cm1100 1gb Xfinitiy NOT GIVING FULL SPEED

[NetworkYT]

Ive Been Using this CM1100 since 2019 And got a new one Bcs the old one had a problom in february 2020 (at the time 250mbps 10mbps Upload) Then In July i got 600mbps 20mbps (Xfinity Obviusly) And now in Novemberi got 1 gigabit plan on 11-15-2020 

And Modem Restarted then i got 200 to 300 After that i replced the modem Nothing replaced my roiter 4 TIMESS! !!!!!!!!!!!!! and nothing the tech came and removed the splitter 

PLEASE HELP/HALP

[FURRYe38]

Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure to connect a Gb ethernet wired PC to the back of the modem on WAN port #1. Remove any external router.
Be sure to disable LAG on the modems web page as well.
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute them back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...