A cashback is a manufacturer campaign which refunds you part of the purchase price. Cashback deals are always handled by the manufacturer rather than Coolblue.
You have to apply for a cashback via the manufacturer. We advise you to contact the manufacturer, since they'll be able to help you.
It's best to contact the manufacturer, because they're going to pay out the cashback.
During the promotion, you can find the promotional terms and conditions and a link to the promotional form or to the website of the manufacturer on the product page. Here, you'll find exactly what you have to do to receive your cashback. You'll always receive the cashback after your purchase, never beforehand. It often takes a few weeks before the manufacturer transfers the amount to your bank account.
If a product has both a discount and cashback, both promotions apply. Note: you'll receive the cashback from the manufacturer afterwards. You have to pay this amount at checkout.