The download speed is stable and quick, yet browsing is exceedingly slow.

For instance, when visiting a website, I often need to refresh the page multiple times before it displays properly.
and when I test my download speed using Speedtest, I encounter an error.Download Test Error A socket error occurred during the download test. A firewall could be blocking the connection or the server might be having some issues. Please try again later.
However, when I download a file, the download speed remains stable without any issues.
Windows 11 64bit fully updated
I tried Edge, Firefox, and Chrome, but encountered the same problem with all three.

If you suspect it to be caused by firewall, temporarily turn of the firewall and test.
Clear the cache in all your browsers.
flush dns cache and restart Flush DNS Resolver Cache in Windows 11 Tutorial