checkout not working

Can you please fix my checkout process for the following shop?
Basically when I buy a product and follow the checkout process and pay for it with the manual transfer it goes to a white screen then I go back and it show the following error message
Looks like you haven't added anything your cart. Let's go shopping!"
which is also a wrong error message.
The product was there but when I try to paid with manual payment (bonifico) it stops and got nothing.
Please try yourself. support access granted.