Slow Page Speed and long LCP

Hello,

All pages of my website have a very slow page speed and the latest tool released by Google (Web Vitals) shows LCP (Largest Contentful Paint) to be more than 10 seconds (one time it showed even 18s).

The PageSpeed Insights tool flags out the following issues:
Eliminate render-blocking resources
Remove unused JavaScript
etc.

It even mentions: “Consider finding a more optimized theme”

I like the ColorMag theme a lot and I wouldn’t like to change it for another theme, but I don’t know how to improve the page speed if the problem lies in the theme itself.

I wonder if you could help me with it and tell me what should I do to improve my speed?

(On images, I use Smush plugin and I also compress each image in tinypng.com before uploading on the site, so I don’t think the main problem lies in the images).

Thank you in advance for your help.

Arthur

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