Windows 10: My PC's loading speed keeps fluctuating

So over the past month, I've had an issue where the loading would be slow when I try to load websites. This wasn't happening before until it suddenly started not to load a website until I waited about 20 seconds. After it loaded, I refreshed the page and it loads instantly. After a few refreshes, the cycle repeats. This happens in games as well as YouTube videos, where the video would download quickly, but after some time, it would stop and interrupt my video. Whenever I booted my computer, everything would work perfectly fine. After about 10 minutes, things would start going downhill as I men

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LAN transfer speed fluctuation

I recently bought a new Win 10 laptop. I transfered my data from my old win7 laptop to the new one via lan cable. But the copying speed fluctuates between 11 MBPS to 200 KBPS. And am talking about a single large file of about 11 GB. I don't get it. I am
not using internet connection and only those two computers are connected via LAN. I just wanna know the reason for such fluctuation.

 

Core speed fluctuation

My core speed and multiplier, according to CPU Z, keeps fluctuating from 1600MHz x6 to 2400MHz x9. What the hell does this mean and what can I do to fix it?

 

Fluctuating Download/Upload Internet Speed - up to 50% less

Hi there. I'm trying to troubleshoot my friend's internet speed that goes from ~150-375 Mbps download and ~15-37 Mbps upload. She's paying for 400/40 and the internet repairman said the speeds going into the modem are fine. She's directly connected (no wi-fi)
and the normal speeds are around 220 down/25 up.

The network card has the latest driver (tried uninstall/reinstall), and I've tried some other things (listed here: Top 5 Ways to Fix Slow Internet after Windows 10 Update | Driver Talent), but it doesn't seem to make a difference.
If it does, the proper speeds don't last long so it just could be a coincidence. I know there is always fluctuation in speeds, but over 50% sometimes is too much.

Thanks.