Some of this is guess work, but the hook should be what you have.
theme-trends-settings_page_gestione-livelli-abbonamento
If you want to do some testing, open the ACF file
advanced-custom-fields-pro/pro/admin/options-page.php
on line 459 you’ll find the function html
function html() {
// add this line to test
echo '<br><br>',current_filter(),'<br><br>';
if you temporarily add the above test code the hook that is being used to display the options page will be output at the top of your options page. I’d be curious to know what it is.