If you are saying that if your AMD Radeon 6800 GPU card should become defective if you can send the GPU for Warranty repairs in Croatia.
What you need to do is open a AMD Warranty Request from here: https://www.amd.com/en/support/kb/warranty-information/rma-form
AMD will tell you how to RMA your GPU card under Warranty. Since you live in Europe I don't know where AMD will instruct you to send the GPU card for Warranty work. You will find out when you open a AMD Warranty Request.
Here is AMD Warranty for the RX6800 and RX6800XT purchased at AMD Store:
