Hello.
Please set Merge stylesheets and critical css in porto>speed optimize wizard>advanced. As you wish, I just generated the critical css for corporate 7.
As you can see below, the performance score is 99.
Please see results.
https://pagespeed.web.dev/report?url=https%3A%2F%2Fwww.portotheme.com%2Fwordpress%2Fporto%2Fcorporate17%2F&hl=en&form_factor=desktop
If you wish to know more about the this functionality, please read the below url.
https://www.portotheme.com/wordpress/porto/documentation/how-to-improve-site-speed/
You can improve any site with this func.
Best Regards.