Hello,
Thank you so much for contacting our support center.
As we can see, your website with Basel doesn’t have any performance issues at the moment. As for the optimization so the most important points are the cache plugin (we prefer WP Rocket), optimize all images, use CDN and don’t have too many plugins that may slow your website down. You can try to disable them one by one to check the performance with and without particular plugins. If you will have any additional questions, contact ask and we will do our best to help you.
Kind Regards
XTemos Studio