How do I fix the url when clicking on portfolio item?

You could do it with jQuery:

jQuery(document).ready(function($) {

    $('a[href*=#]').on('click', function(event){     
        event.preventDefault();
    });

});

Save that to a file (something.js) and upload it to your server. Then add the following to your functions.php (remember to set up a child theme if you aren’t using one):

add_action( 'wp_enqueue_scripts', 'prefix_load_scripts' );
function prefix_load_scripts() {
    wp_register_script( 'something', get_stylesheet_directory_uri() . '/path/to/file/something.js', array('jquery'), true );
    wp_enqueue_script( 'something' );
}