The Internet on a PC does not rise above 60Mbps, but should give out 300Mbps. What's wrong?

Question

Computer networks

My PC does not give out a speed of more than 60Mbps, although my tariff is up to 300Mbps. The entire Internet climbed already installed 1gbit with duplex and changed the bandwidth, etc. nothing helped. A specialist came, everything worked on his laptop, but he couldn’t do anything to me, he said to reinstall Windows, but nothing has changed. Could there be something wrong with the network adapter?

Answer 1

Check if the problem is reproduced in other OS other than Windows.
linux, android on the phone...
turn off QoS in the network card settings
, make sure that on the router, switches - gigabit ports, not 100 mbps.
make sure the cables have 8 cores and not 4.

Answer 2

Try to set the maximum sizes of rx/tx buffers in adapter settings. If it doesn't help, then alas...
Cheap Realtek network cards differ from Intel in that they are software rather than hardware ones.