The code for carousel vertical is in templates\listingslider.php file.

Images are resized using resize rule: listing_full_slider.

To remove the resize rule for images must edit templates\listingslider.php and replace above resize rules with full.

Next must add below css in Theme options – Design – Custom CSS :

#carousel-listing {
height: 500px!important;
}
.slick-track {
width: 825px!important;
height: 500px!important;
}
.slick-list {
height: 500px!important;
}
.row_slider .col-md-9 {
height: 600px;
}

#carousel-listing-nav {
height: 81px;
}

.slick-initialized .slick-slide img {
height: 100%;
width: auto;
margin: 0px auto;
}
#carousel-listing-nav img {
height: 78px;
}