Hello, @jonathantan,
Thanks for purchasing and using our theme.
We would like to suggest you to please read and follow the instructions written in our theme documentation here: https://www.portotheme.com/wordpress/porto/documentation/faq/site-distort-because-of-mixed-content-ssl-certificate-issue/
We are confident that this will help you in resolving your issue.
Best Regards,
PThemes Team.