Clarify "his max.....".
More information is needed.
For most residential users the network connection path is as shown by the following line diagram:
ISP ---coax/DSL---> Modem ---ethernet --->[WAN] Router [LAN] ----ethernet ---> computer and/or ~~~ wireless ~~~> computer.
There may be other devices connected as well; printers, NAS, Gaming devices, etc.
Another common configuration is that the modem/router are combined as a single device.
The network will only be as fast as the slowest component.
In any case, please update your post to add detail about the present connections and be sure to include make and model information.
Who has full admin rights to the router and other network devices?
The slow performance may be due to hardware, software, or configuration problems. Or just a faulty cable....