Why my wp_posts data is so huge?

I don't think Visual Composer is the problem. Have you installed a logging plugin?

Open phpMyAdmin and simply delete them. They are likely a post type you dont use.

You can use the following query

DELETE po,pm,tr
    FROM wp_posts po
    LEFT JOIN wp_term_relationships tr
        ON (po.ID = tr.object_id)
    LEFT JOIN wp_postmeta pm
        ON (po.ID = pm.post_id)
    WHERE po.post_type = '{{Suspected post type}}';

Make sure you don't remove the posta that are used by your site. Check what post types you use.

Also 'attachment', 'post', 'page', 'revision', ' nav_menu_item' so on are WordPress default - don't remove them.

No, that isn't normal for 23 posts.

Note that "posts" is pretty wide concept in modern WordPress. Many things are posts without being obvious as such, for example parts of navigation menus.

While 60k entries does sound excessive for a small site, there is no telling without examining actual data to determine which post types it belongs to and if those entries are valid for some purpose or merely broken leftovers.