Google Page Speed Score Problem

Hi,

I'm facing a problem to setup Hummingbird Pro plugin for Google Page Speed opportunities. I don't know how to work with Eliminate render-blocking resources, Defer unused CSS, Serve images in next-gen formats, Defer offscreen images & Reduce server response times (TTFB).

Site Link: https://vivortho.fr/

I did the basic optimizations from Hummingbird Pro. But my google page speed score is very low. So, I want to fix page speed and I need the green score.

Please, give me instruction to fix page speed opportunities to optimize.