Owl carousel item content z-index

I have a issue with setting z-index of owl carousel item content over fixed overlay.

Every carousel item has background image and text content.

Fixed overlay should be over item (background image), but not over item content.

Fixed overlay cant be part of carousel item, it has to stay static when slides are changing.

What i have:

What i want:

I tried all different approaches, from various z-index values together with different positioning of all elements, but with no success.

HTML, PHP:

<div class="intro">

    <div class="owl-carousel owl-theme">
    <?php
    foreach ($Services as $key => $service) {
        echo '<div class="item ' . $key .'" style="background: url(' . $css_path . $service->img_mainpage . '">';
            echo '<div class="hdr_main"><a href="/' . slug($service->title) . '">' . $service->title . '</a></div>';
            echo '<span class="about">' . $service->about . '</span>';
        echo '</div>';
    }
    ?>
    </div>

    <div class="fixed-overlay">
        <?php include(__DIR__ . '/../../assets/gui/mainpage-polygon.svg'); ?>  
    </div>

</div>

CSS:

div.intro {
    position: relative;
    height: 100vh;
    background: rgb(0, 121, 201);
}

div.intro .fixed-overlay {
    position: absolute;
    top: 0px;
    left: 0px;
    height: 100vh;
    width: 60%;
    z-index: 3;
}

.owl-carousel {
    height: 100vh;
    z-index: 2;
}

.owl-carousel .item {
    height: 100vh;
    display: flex;
    justify-content: center;
    flex-direction: column;
    text-align: right;
    padding-right: 13%;
    background-repeat: no-repeat !important;
    background-size: cover !important;
    background-position: center center !important;
}

.item .hdr_main a {
    z-index: 9999;
}

Thank you.