Станислав

.col-lg-4 {
    position: relative
}
.col-hide {
    position: absolute;
    background: #ddd;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    opacity: .3;
    z-index: 2
}

<div class="row">
      <?php foreach($actionArr as $action){ ?>
            <div class="col-lg-4 col-md-6 mb-4">
                <?php if ($action['rezerved']) { ?>
                    <div class="col-hide"></div>
                <?php } ?>

window.onscroll = function() {
	var scrolledX = window.pageXOffset,
		scrolledY = window.pageYOffset;
	if(scrolledX) {
		$('.header').css({
			"marginLeft":"-" + scrolledX + "px"
		});
	} else {
		$('.header').removeAttr("style");
	}
}