Google Analytics can’t track visits

First, you should know that WP Fastest Cache does not modify any 3th part js source.

I checked the html source of your site and I saw that there is no google analytics code on the html source.

Hi, maybe i was editing something during your check.
GA4 is present with Google Site Kit notation:

<!-- Snippet Google Analytics aggiunto da Site Kit -->
<script type='text/javascript' src='https://www.googletagmanager.com/gtag/js?id=GT-P8VC***' id='google_gtagjs-js' async></script>
<script id="google_gtagjs-js-after" type="text/javascript">
window.dataLayer = window.dataLayer || [];function gtag(){dataLayer.push(arguments);}
gtag('set', 'linker', {"domains":["studiolegaleasmahi.it"]} );
gtag("js", new Date());
gtag("set", "developer_id.dZTNiMT", true);
gtag("config", "GT-P8VC***");
</script>
<!-- Termina lo snippet Google Analytics aggiunto da Site Kit -->

I saw the code but it is not a analytics code.

This is the new way Google SiteKit (official) Sets code for Google Analytics 4 (GA4) using google Tag Manager.
And now analytics are working with that code (deactivating WP Fast Cache)

wp fastest cache does not modify any 3th party js source.