Cache pages in background

A similar need of cache saving is needed on one of my websites: www BKGSU com

Need help.
HOW to “Specify a cache validator” to images, using Corvid?

I used page speed test tools like GtMetrix, Pingdom, PageSpeed, etc. and I found GtMetrix begin most ‘wix friendly’. It gave 88/100. While Google’s pagespeed is worst, giving only 35/100 (on Desktop) while saying the site is interactive after 5 seconds. That’s false. In real, the site performs well.

Lastly, I found Pingdom tools to be ‘in-between’ as it gives 80/100 on average. While it always points out that ‘‘images missing cache validator’’