Thank you @lu.diehl
The code below worked for me, but there is a gray area under banner. How could I get rid of this?
https://puurakentajat-2020.squarespace.com/
pasword. clt321
.sqs-block-horizontalrule {margin-top:-25px !important; margin-bottom:-25px !important;}
.footer-inner { padding: 24px 22px; }
.collection-type-page.has-promoted-gallery #promotedGalleryWrapper .sqs-block,
.collection-type-page.has-promoted-gallery .promoted-gallery-wrapper .sqs-block,
{
max-height: 500px!important;
}
.sqs-gallery-design-stacked-slide {
height: 500px!important;
}