Hey @radualunita,
I believe you’re using the latest version of PHP. If that is the case, please try downgrading a version older like PHP 7.4 to PHP 7.0 and see if that removes the warning.
PHP warnings just warn that a function could be deprecated in the future. But, that doesn’t mean that there would be problems. Our development team will eventually update the codebase to eliminate warnings for the latest version of PHP.
You can either downgrade or just hide the PHP warning (recommended for live sites) by setting WP Debug in wp-config.php to true and then adding the following lines of code below that. Your web host might be able to help you with this. If not, just hire a developer to do this for you.
// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', true );
// Disable display of errors and warnings
define( 'WP_DEBUG_DISPLAY', false );
@ini_set( 'display_errors', 0 );
Hope that helps.