Hi there,

By default WordPress will apply the blog slug to every post type so to disable this you have to add a code to the functions of the child theme.

Can you try adding this code to the functions.php of the child  theme:

/**
 * Set 'with_front' to false for the 'portfolio' post type.
 */
add_filter( 'register_post_type_args', function( $args, $post_type )
{
    if( 'portfolio' === $post_type && is_array( $args ) )
            $args['rewrite']['with_front'] = false;
    return $args;
}, 99, 2 );

And then add the news under permalinks so it will be applied only in the blog posts and not the whole site.