To Fix it follow this tutorial

First,

1.Create a new .php file in the wp-content/mu-plugins folder. Like name it elementorfix.php
2. Add this code snippet below to the file you just created

Second, use below code

<?php
/**
 * Plugin Name: Elementor Scheme_Color and Scheme_Typography Class Issue
 **/

namespace Elementor;

\add_action(
  'plugins_loaded',
  function() {
    if ( ! class_exists( 'Elementor\Scheme_Color' ) ) {
      class Scheme_Color extends Core\Schemes\Color {}
    }
  }
);
\add_action(
  'plugins_loaded',
  function() {
    if ( ! class_exists( 'Elementor\Scheme_Typography' ) ) {
      class Scheme_Typography extends Core\Schemes\Typography {}
    }
  }
);
?>

Source : Collected