Expires headers, Defer parsing of JavaScript, Caching Speed Help

I would like assistance with training on how to improve the following for a Wordpress site.

1. Add Expires headers,
2. Defer parsing of JavaScript,
3. Leverage browser caching

I need assistance with the above as those scores are poor in the GT Metrix results. No matter what plugin I try and I have tried at least 10 of them. I cannot seem to improve this score. The server end all settings are 100% correct to improve the above 3 but it still does not help.

I have plenty of experience in all kinds of speed plugins and been working with Wordpress for over 10 years.
I have the site in question setup on Cloudflare CDN and with Fastcomet FastCloud Extra so server end and speeds are supposed to be super fast.

I am currently trying W3 Total Cache, it is not helping.
I do not want to use any paid for Cache plugins as I have done this in the past and they do not work.
The site is setup on Wordpress with Avada theme.

Current speeds are
PageSpeed Score
(81%)
YSlow Score
(69%)
Fully Loaded Time
18.5s

I want Page Speed to be over 95%
I want Yslow score to be over 90%
I want fully loaded time to be under 3 seconds.


I am looking for someone to train me how to improve on the above items to improve speed to be GT Metrix speed scores without breaking the site. Also if software , plugin, theme updates are run, it must not loose site speed optimization.

I run a digital agency and manage over 100 websites, if you can help me with this and are excellent at what you do re wordpress speed iptimization, we can discuss further business.

I look forward to positive responses. Thank you