How to darken Z-index in CSS?

Question

css

My problem is that when the application block opens in it, all Z-index objects are not darkened, but the whole site does it. How to fix such an error?

#overlay {
    width: 100%;
    height: 100%;
    position: fixed;
    top: 0;
    left: 0;
    display: none;
    background: #000;
    opacity: .8;
}

Answer 1

z-index ?

Answer 2

you need to correctly set the z-index to
the blocks that are on top should be larger, so that below them below. moreover, for all elements where the z-index is, you need to prescribe a position other than static