I hate advice like that suggesting network negotiation speed or lan drivers, is it rarely ever to do with either of them, leave negotiation on auto. If auto is not working then it's something else. Unless having issues with 2.5gbe with gigabit routers then changing negotiation speed might work in that case.
Your issue is more likely network cable or router/switch. If router or switch (if use a switch to extend network to other devices) are gigabit then it's the cable. There's no such thing as cat 7 or higher network cables, if you had one these, they are fake afaik. Your typical cat 5e or 6 is fine.
For gigabit negotiation to work, all 8 wires must be in good condition. If one wire is dodgy negotiation speed drops to megabit which is 4 wires.