How to use Filter for author email and author Description

I want ti use filter for author email and author description to use them from the custom frield.

Here is my rough code but now wokring:

/** change the email of author  **/
add_filter( 'the_author_meta', 'guest_author_email' );
function guest_author_email( $emailt ) {
global $post;
$authore = get_post_meta( $post->ID, 'gp_email', true );
if ( $authore )
$emailt = $authore;
return $emailt;
}

Where gp_email is the author email taken from the custom field.

Original concept of code taken from this post: