When you have ACF User fields like first name and last name and you need to keep that in sync with what is entered in WordPress user profile (works both ways)

acf_sync_with_user_profile.php

//If both changed at the same time - custom field value will be applied as it fires later, set 30 to change it add_action( 'profile_update', array($this, 'update_acf_fields'), 30, 2 );
class Sync_ACF_with_User_Profile_Class {
	static public $sync_pair = array(
									array(	'acf' => 'member_name', 'profile_field' => 'first_name'), //add acf field name according to your setup
									array(	'acf' => 'member_lastname', 'profile_field' => 'last_name')// add more rows to sync any other fields as well
									);
    public function __construct() {
		 add_action( 'profile_update', array($this, 'update_acf_fields'), 10, 2 ); //when profile is updated -> update ACF
		 add_action('updated_user_meta',  array($this, 'update_user_profile_fields'),10,4); // when ACF is updated -> update profile
		 add_action('added_user_meta', array($this, 'update_user_profile_fields'),10,4); // when ACF is added -> update profile
    }	
	
	public function update_user_profile_fields($meta_id, $user_id, $meta_key, $meta_value){			
			$user_data = get_userdata( $user_id );
			foreach (Sync_ACF_with_User_Profile_Class::$sync_pair as $sync_pair){
				if ($sync_pair['acf']  == $meta_key ){
					$profile_field = $sync_pair['profile_field'];
					$profile_field_value = $user_data->$profile_field;
					$update = ($profile_field_value == $meta_value) ? false : wp_update_user(['ID' => $user_id, $profile_field => $meta_value]); 
				}				
			}	
	}
	
    public function update_acf_fields( $user_id, $old_user_data ) {
			$user_data = get_userdata( $user_id );
			foreach (Sync_ACF_with_User_Profile_Class::$sync_pair as $sync_pair){
				$meta_value = get_user_meta($user_id, $sync_pair['acf'] , true);
				$profile_field = $sync_pair['profile_field'];
				$profile_field_value = $user_data->$profile_field;
				$update = ($profile_field_value == $meta_value) ? false : update_user_meta($user_id, $sync_pair['acf'], $profile_field_value );
			}
	}	
}

$sync = new Sync_ACF_with_User_Profile_Class();
add_action( 'wp_loaded', array( $sync, '__construct' ) );