That's the correct behaviour according to VirtueMart when a user returns from the external payment page back to the shop.
It allows to call the payment plugin, process the order information and inject the additional data to the layout. I have it also on your website:
Vă mulţumim pentru comanda dumneavoastră!
Your order #TY1B01578 has been successfully processed.
Sandbox Mode is enabled, no real money are transferred. Sandbox is used to test the payments.
View order
The problem is, that it is being displayed below all modules you have, because the VirtueMart component body is displayed there...
And /cart?task=orderdone is needed to render the page after completing the order, where payment plugin displays the information and redirects you to the payment page.
Kind regards,
Dmitrijs