Server response time increased from 0.2s to 1.3s

After connecting to CF, the server response time of my website increased from 0.2s to 1.3s or more. Tried whatever I could, but still, the problem is there. How can I decrease the server response time?

Here is the link to GTmetrix analysis on a properly optimized post: GTmetrix Analysis

Where is your host server located?

Singapore.
But does it really matter? This is the reason I’m using a CDN

It definitely does. The page source still has to come from your origin server. The GTMetrix test was run in Dallas, TX, USA, so it has to go halfway around the world to get your page source.

The results from fastorslow.com demonstrate this:

I thought this is reason we use CDN.

Btw, when the CDN is disabled, then the server response time is 0.2s to 0.3s. Then why enabling the CDN increases the time? The distance doesn’t increase.

This should explain the Cloudflare network:

Now what should I do to improve the speed performance of my site?