Hello,
01. Please deactivate all the 3rd party plugins and activate only theme-required plugins on the site and then check the issue. I am sure your issue will be solved. Then Activate the 3rd party plugins one by one and check which plugin is creating the issue for you.
Otherwise, if the issue still exists, then keep the 3rd party plugins deactivated and share the WP admin login details of your site so I can check and give you a possible solution.
02. Our theme is optimized for speed and should not significantly slow down your website. However, it’s possible that your website’s performance is affected by the content you have added. For instance, the use of too many plugins, large unoptimized images, or other resources can slow down your website.
We recommend that you remove any unnecessary plugins and install a JS & CSS optimization plugin such as WP Rocket. Our guide on how to optimize your website using our themes can be found here: https://xtemos.com/wordpress-performance-optimization-the-ultimate-guide-in-2021/.
Best Regards,