how to apply paypal discount on cart total?

Array
(
    [return] => http://www.example.com/
    [cancel] => http://www.example.com/
    [currency] => EUR
    [total] => 38.8
    [shipping] => 6
    [tax] => 2.85
    [itemTotal] => 29.95
    [items] => stdClass Object
        (
            [1] => stdClass Object
                (
                    [quantity] => 1
                    [name] => Item one
                    [IDFull] => 1
                    [priceFull] => 32.8
                    [tax] => 2.85
                    [price] => 29.95
                    [priceWith] => 32.80
                    [attributes] => Array
                        (
                        )

                    [ID] => 1
                )

        )

)

This is my sample array for paypal checkout. How to add discount (eg. 20€) on card total price? I have tried many ways, but can't find it out. Thanks!

You can try to add the discount as an item, as I wrote here.