Understanding GTMetrix Waterfall Chart

Hey there, I hope you are able to help me with my site’s loading time issue.

So I’ve always been coming back to my website’s speed, and it’s always seemed to be an issue.

Over time I’ve improved and improved but still have issues with long and inconsistent loading times when testing it with GTMetrix.

The site I am trying to optimise for speed is https://successfularchistudent.com/
When I run a GTMetrix test, the results show long purple bars in the waterfall chart. I understand that this is “waiting” time but I am unsure how to optimise this. Perhaps it has something to do with setting up Cloudflare?

I use W3 Total Cache and just got Cloudflare to attempt to boost the site’s speed but still experience anywhere from 4-9 seconds loading time, and yes, each test seems to vary that much.

My PageSpeed score is 87% and YSlow 73%, which is better than what I previously had but obviously I’m still missing something.

Any help would be extremely appreciated, thank you in advance!
Kind regards,
Kyle.

The page I need help with: [log in to see the link]