Thank you so much for your help.

I ran the tools on the network tab for the pages.aspx page, and here's what I got. BTW, the server is on my local network, and my external speedtest at my desk are 600Mbps up and down.

Wait - duration <1ms
Start - duration <1ms
Request - duration 7.95s
Response - duration 1.18s
Gap - duration 20.03s

On the summar it says I received 5.74MB. And time taken is 9.14s. Why such a large amount of data?

Does this information indicate it's on the server?

High TTFB means the server needs long time to respond to your request and deliver the page, i.e. the issue is on the server side.
if the same site performs better (I wouldn't say good to 4s) on a local install, there must be an issue in IIS website configuration.

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Cheers from Germany,
Sebastian Leupold

   

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I ran a test on another portal in this site with just a few pages, and it's ttfb is only a few hundred ms. Does this still indicate IIS settings?