You mean the author box when an author’s posts are listed on the front end? Not the author meta box on the post edit screen?
It depends on how your theme displays the box to start with. We can’t know this with commercial themes. Anyway, you would wrap that display part in a conditional that might look something like this:
global $authordata;
if ( 1 != $authordata->ID ) {
// the theme's author box output code
}
This would be typically the author.php template, but theme’s vary in their use of templates. It also assumes the first post is retrieved to determine the author and set the $authordata
global before rewinding back to the beginning. Again, themes vary how this is done.
My understanding of ThemeForest themes is they are difficult to safely customize because they are implemented as child themes of a generic core theme. Being already a child theme takes away your opportunity to make your own child theme that would protect your customizations from theme updates.
(if you did mean the edit screen metabox, conditionally enqueue some CSS to hide it when the current user ID == 1)