Your purchase will be on whichever shop systems you purchased it from.
Return it to the shop if you bought it that way.
Or contact the online Shop if you bought it that way.
A copy of the receipt may have been emailed to you.
Current Phone ~
Samsung Note 20 Ultra 5G SM-N9860_256Gb SnapDragon 865+
Samsung One Ui 3.1/ Android 11.
@Armin1969 Welcome to the Samsung Community! If you've had the s8 within 30 days we would recommend speaking to your retailer to discuss your returns options. We're also happy to help troubleshoot and fix the problem too.
When you mention screen problems, can you explain exactly what's happening please?