Enabling full duplex on modem

Thanks for answer! I tested connection on PC, phones and laptop and result is always 100mb/s on wired connections and 350mb/s on wifi- which is acceptable ( paying for gigabit net :)) for me but i would like to have same speed also on wires.

Hello

First check the quality of your ethernet cables (cat 5E minimum is required for gigabit)  or replace them with new ones, and prefer cat 6 cables. 

Also check if the network adapters of your PCs are compatible gigabit ethernet (1000 mbps) and not only are fast ethernet (100 Mbps) . 

Test directly on the modem without going through other network components like switches, Powerline adapters or other router

Hello @Brus,
The good old Ethernet cable is the safest way to connect to the internet and enjoy the highest speeds.
The problem may come from the RJ 45 Ethernet cable. Change the cable to a certified gigabit Ethernet Category 5E (or higher).
I invite you to test and come back to me if the situation remains unchanged ;)
Have a good day