I hope you are well today and thank you for your question.
Would you mind if I log in to your site and do quick troubleshooting? If this is ok then could you please temporarily create an admin user account and share the account login details privately by adding them in the box having text “Enter your private content here (only you and forum moderators will be able to see it)”?
The home page on your website is created using the Elementor page builder so please edit it using the Elementor page builder and not WPBakery page builder to add the slider.