Troubleshooting Internet connection, PC "can" connect to Internet, but can't browse normally

I need to troubleshoot what's happening in my network for the past two months. I don't even know what the cause could be. So, two months prior, when I was just using my computer as usual, the internet was suddenly cut off. It was normal since I live with bad ISP uptime. But I tried my usual solution of resetting, restarting, and seeing if the DNS is up. I couldn't find the cause, so we called the ISP to troubleshoot it. They came, suddenly it worked again without them doing anything to it. I figured that it's just a coincidence. They went back and I did my thing again. One night, there was a h

Question by spitfire on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.