PageSpeed complains on Mobile

Hi,

I activated WP-Optimize on my site. Pages are cached (preloaded), CSS and JS minified. (Images are served by EWWW).

When I check the website speed with Google’s PageSpeed, the desktop version is fine, but it strangely complains with the Mobile version. The First Contentful Paint requires almost 4 seconds.

The first reported render-blocking resource accounting for 1.2s : minified css
And the second reported one accounting for 0.8s: minified js

What’s totally puzzling to me is that happens only on the Mobile version of the test, the Desktop flies at 97 points in performance, while the mobile is at 79.

What can I do to fix this situation ? (It happens that a sizeable proportion of the visitors use their mobile, of course.)

Thanks for your insights,
Regards

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