At 3 megabit you don't have spare to share.
My mother's internet becomes slow usually only in the wee hours of the morning, but every morning. SpeedTest shows the correct speed she is paying for (3 Mbps) which is fine as she watches no videos, streams nothing, just light browsing. The most taxing game she plays online is a crossword.
If she goes into safe mode the browser/internet is fast (relatively) again and as she exits into regular bootup it is fine also for a while then returns to so slow it's not worth using.
tried: system restore, java updates, OS updates, browsers Edge and Firefox
info: Router/modem is Cisco model DPC3941T with wifi, phone ports and 2 RJ 45 ports
uses Windows 10 Home
NIC is RealTek PCIe GBE family controller
Any help is appreciated greatly.