Override functions and template

Hello,

I need to change the “Default Wishlist” text in get_multiple_wishlist function in /wish-list-for-woocommerce/includes/class-alg-wc-wish-list-ajax.php, I try to override this function in my child theme in functions.php but it doesn’t work, this is my code :

if (class_exists('Alg_WC_Wish_List_Ajax')) {
    remove_action( 'wp_ajax_alg_wc_function', array( 'Alg_WC_Wish_List_Ajax', 'get_multiple_wishlist' ) );
    remove_action( 'wp_ajax_nopriv_alg_wc_wl_function', array( 'Alg_WC_Wish_List_Ajax', 'get_multiple_wishlist' ) );

    $new_alg_wc_wish_list_ajax_instance = new Alg_WC_Wish_List_Ajax();

    add_action( 'wp_ajax_alg_wc_function', array(  $new_alg_wc_wish_list_ajax_instance, 'get_multiple_wishlist_new' ) );
    add_action( 'wp_ajax_nopriv_alg_wc_wc_function', array(  $new_alg_wc_wish_list_ajax_instance, 'get_multiple_wishlist_new' ) );
}

function get_multiple_wishlist_new() {
...
}

What is the problem in my code, why it doesn’t work ?

Next, I try to paste the template wish-list.php, I paste this in child_theme/plugins/wish-list-for-woocommerce/templates/wish-list.php, to change the text “Default Wishlist” but it doesn’t work,

Do I need to add something in my functions.php ?

Thank you,

Regards,