Internet browsing is slow without VPN and often get 404 error

I am subscribed to 12mbps cable internet, but on my laptop the connection is dead slow when browsing. I am connected to the Wifi of the router my service provider gave me. The connection speed is okay on my Tablet or Phone from the Wifi, the problem occurs on the laptop only. Most of the pages I want to visit load very very slowly, and very often I get 404 error first, then, after 15-20 seconds the page starts to load. Oddly, when I use VPN connection of a third party provider, the connection becomes lightning fat compared to the speed without VPN.

As the problem only occurs on both of my laptops installed with Windows 7, I started thinking about whether it can be a problem with my operating system components. On both laptops, I am running the fresh, unupdated Windows 7 Ultimate. From the beginning I disabled svchost, so there are no annoying updates. Is it possible that this way I skipped an update that has an effect on network connection, and that's why I have this problem?

I run Eset Nod Virusscanner on both of my laptops, they didn't report any infections or suspicious activity so far going on my machine.

Any ideas to solve the issue?

I'm sure other people will help but it sounds like you don't have all the Windows updates installed. I would install all that are available first, in case one of them affects your problem in a good way. Since Win 7 support ended Jan 14, there should be no updates to worry about once you install the others.

I don't know which browser you're using but it's possible you have the security settings set too high.

Try changing your DNS to a 3rd party provider such as cloudflares 1.1.1.1 or Googles 8.8.8.8

DNS Addressing - How to Change in Windows 7

I set Google's, it seems to be fine now. I will test it further and will come back to report what happened.