Ahoj Milan,

Try that Custom CSS

@media screen and (max-with: 580px) {
.sppb-carousel-extended-item img 
{width: auto;object-fit: cover;height: 100%;margin: 0 auto; max-width: 150px;}  
}

add it, for example, inside Page Setting > Custom CSS

Hello,

I didn't use css because it doesn't work. I found that the SP Page Builder administration doesn't display the image size preview for mobile phones correctly. That's why I set the default image height to 150 px. I've changed it to 230 px and it's OK on mobile. The administration should fix it.

Best regards, Milan