Hi SANDINO,
When you sell products through dropshipping, the products are delivered directly to the customer, so in this scenario it will be your customer who will pay for the custom fees/taxes.
As far as I know there is no way to prepay your custom fees.
But you can add a note to your listings stating the origin of your products, this will help give your customers an idea that they may incur additional fees when their orders are delivered to them.
Hope this helps.