Cart Is Not Been Emptied

I cant seem to empty the cart after confirm status (the checkout configuration is set to Clean cart when order is confirm and im sure order has been set to confirm)

I elso tried to clean manualy by "$this->removeCart = true;" at the OnAfterPaymentConfiguration() and at OnPaymentNotification() but both does not work.

What should i do?

That's normal. When you are in that mode, you need to redirect the user to the after_end task of the checkout controller (like all the other payment plugins do) when the payment is successful.
Normally, the payment gateway allows you to provide a success url in onAfterOrderConfirm.

For example, in the paypal payment plugin, you have the code:
$return_url = HIKASHOP_LIVE.'index.php?option=com_hikashop&ctrl=checkout&task=after_end&order_id='.$order->order_id.$url_itemid;

Great its working now, but i noticed that when i am redirecting to a thank you page with this parameters (Success URL), then i get only Joomla! thank you for purches and the cart is still in the same condition, only when i move to a different page it's been emptied.
What can i do to display my page without the Joomla! thank you and to visiable the cart at the same page as empty?

Thanks in advance.

You need to add a return url option, like there is for all the other payment plugins.
The task after_end of the checkout controller will automatically redirect to the URL specified in that option if anything is entered there.