Hey @arminunruh thanks for the answer !
But I described it a little unclear, i'm sorry. I didn't want the overlay page to fill 100% of the page, but only, lets say, 95% in height.
i guess in the style css it would mean a different max-height-value, like this
.lay-overlay > .lay-content {
background-color: white;
overflow-y: auto;
max-height: 95vh;