Update KwixoFrontController.php

$_SERVER['REMOTE_ADDR'] replaced by Tools::getRemoteAddr()

$cookie = Context::getContext()->cookie;
$cart = new Cart($cookie->id_cart);
replaced by
$cart = Context::getContext()->cart;

$customer_gender == $male_gender ? 'Monsieur' : 'Madame'
For Kwixo, if it's not a man it's automatically a woman