Restircted currency for payment, but not for shopping cart

[undecided]

I have a maybe unique question/problem.

If PayPal is used for paying, I only want to accept a specific currency when the payment is processed.
Currently I make the same thing on a PrestaShop 1.6 with the old native module. The customer can shop in all available currencies (eg. USD, AUD, CAD, EUR, CHF), but when pressing on "Pay with PayPal" at checkout, the amount the customer is being charged is always AUD (which means that I only receive AUD payments from PayPal).

If I select AUD as restricted currency in TB, the PayPal module does only appear when AUD is selected by the customer in the FrontEnd. If the customer shops with EUR, PayPal does not appear and if I set "customers currency" under currency restrictions, the customer can pay with all available currencies which I do not want to happen.

Is there a way to achieve this or do I have to use the old PS module?

[undecided]

Update: If I set "Shop default currency" then the PayPal module appears at any time regardless the currency someone has selected on the website. So that little part is solved.

The main problem still exists. The customers jumps to PayPal and the amount to pay will be shown in his selected currency and not in AUD. When the customer then tries to pay he gets the message that the currency is not supported, which is correct but not what I want and also not very helpful as the customer will get no information which currency is supported.
I "simply" want that the customer sees AUD on the payment page of PayPal no matter what currency he has selected in the shop.

Any ideas how to achieve this.