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