Thanks Jak, Is this also the reason at the image banner? And how does i change it exactly? aspect ratio too? 16:9 or 4:3?

I saved them as web on photoshop, so they are PNG

Hi guys, My name is Robin. I have some frustrating problem with my store, my image banner stays blurry, even on high resolution now i have 2400 / 1350 and I even tried 1920x 1280. This needs to be simple but Its not. What do i do wrong, and can some ...