Hello,
1/ Temporarily disable the WPBakery plugin and check pages of products and categories. If all is fine, you do not need to edit the content using Elementor.
2/ It is recommended to run import on fresh WordPress installation. If you are not ready to reset all content and start from scratch, we can help you with the import of particular demo pages. Provide URL of demo pages and temporary wp-admin access to your site.
3/ Do you mean slider on your Home page? I can see it from mobile. Please clear cache and check one more time. Describe the problem in more detail, please.
Regards