The new blocks Gutenberg editor that comes with WordPress 5.0 has created a conflict with visual composer. As a user of WP Bakery Visual Composer, you might find it difficult to edit your pages after this update.
The solution to this problem is to simply install a new plugin that enables the classic editor and will put your Visual Composer back in order.
You can get the plugin Here: https://wordpress.org/plugins/classic-editor/