@font-face {
    font-family: 'open-sans';
    src: url('/font/opensans-variablefont_wdthwght-webfont.woff2') format('woff2'),
    url('/font/opensans-variablefont_wdthwght-webfont.woff') format('woff');
    font-weight: normal;
    font-style: normal;
}
*
{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
html, body {
    min-height: 100%;
    width: auto;
}

.logo {
    width: 100%;
}

button {
    display: inline-block;
    position: relative;
    top: -45px;
    width: 222px;
    height: 35px;
    padding: 5px 14px 0 18px;
    background-color: #a2dc3c;
    background-image: linear-gradient(to bottom, #a2dc3c 0%, #81b427 100%);
    border: none;
    color: #fff;
    border-radius: 5px;
    font-size: 16px;
    font-weight: 700;
    cursor: pointer;
    font-family: open-sans, sans-serif;
}

.main {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}
.main-content {
    text-align: center;
    font-family: open-sans, sans-serif;
    font-size: 15px;
    padding: 0 20px;
    line-height: 30px;
}

a { color: #80b529 }


.content {
    margin-top: 30px;
}
.coy-logo {
    position: relative;
    display: inline-flex;
    max-width: 200px;
    top: -10px;
}

.tavarlin-logo {
    position: relative;
    margin: auto;
    height: auto;
    top: -50px;
    max-width: 180px;
}
.keto-logo {
    position: relative;
    height: auto;
    top: -50px;
    max-width: 140px;
}
.bottom-logos {
    display: flex;
    flex-direction: column;
    justify-content: center;
}
.footer-nav {
    width: 80%;
}

.footer-nav li {
    padding-inline: 4px;
}

.bottom-nav {
    list-style: none;
    display: flex;
    justify-content: end;
    margin-top: 16px;
    margin-bottom: 16px;
}

h1 {
    margin-bottom: 20px;
    font-size: 25px;
    line-height: 16px;
}
h2 {
    font-size: 20px;
    margin-top: 40px;
    margin-bottom: 40px;
}
h4 {
    color: black;
    margin-bottom: 12px;
    font-size: 20px;
}

h5 {
    font-size: 16px;
}

p {
    display: block;
    margin-bottom: 24px;
}

li {
    padding-left: 20px;
    margin-bottom: 10px;
}

.impressum-content {
    font-size: 15px;
    line-height: 24px;
    margin: 0 auto;
    padding: 0 22px;
    position: relative;
    width: 80%;
}
.impressum-content .footer-nav,
.datenschutz-content .footer-nav
{
    width: 100%;
}
.content-area {
    margin-top: 25px;
}
.datenschutz-content {
    font-size: 17px;
    display: block;
    line-height: 24px;
    margin: 0 auto;
    padding-left: 22px;
    list-style-position: inside;
    width: 75%;
}
.datenschutz-text {
    margin-top: 25px;
}
hr {
    border-top: 1px solid #a2dc3c;
}
header.header {
    display: flex;
    justify-content: center;
    align-items: center;
    margin-inline: auto;
}
/* Bigger screens */
@media screen and (min-width: 800px) {
    .logo {
        transform: translate(0px, 30px);
    }

    .main-content {
        font-size: 24px;
        line-height: 50px;
    }

    .content {
        margin-top: 55px;
        margin-bottom: 20px;
    }

    .bottom-logos {
        position: relative;
        display: flex;
        flex-direction: row;
        align-items: center;
    }

    .coy-logo {
        max-width: 400px;
        margin-top: -10px;
    }

    .tavarlin-logo {
        max-width: 328px;
        margin: 0;
    }

    .keto-logo {
        max-width: 300px;
    }
    button {
        display: inline-block;
        width: 400px;
        padding: 8px 12px 8px 12px;
        top: -15px;
        margin-bottom: 40px;
        background-color: #a2dc3c;
        background-image: linear-gradient(to bottom, #a2dc3c 0%, #81b427 100%);
        border: none;
        color: #fff;
        border-radius: 5px;
        position: relative;
        font-size: 20px;
        font-weight: 700;
        cursor: pointer;
        font-family: open-sans, sans-serif;
    }
}
/* Landscape */
@media screen and (min-width: 480px){
    .logo {
        display: inline-block;
        text-align: center;
        max-width: 320px;
        transform: translate(0px, 8px);
    }
    .img-container {
        display: inline-flex;
        flex-direction: row;
        margin: 0 40px;
        max-width: 800px;
    }
    button {
        top: -35px;
        width: 300px;
        height: 35px;
    }
}
<!DOCTYPE html>
<html lang="de">
<head>
    <meta charset="utf-8">
    <title>Nu Prevento</title>
    <link rel="stylesheet" type="text/css" media="screen" href="https://stackoverflow.com/questions/73055053/css/normalize.css">
    <link rel="stylesheet" type="text/css" media="screen" href="css/style.css">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="IE=edge"/>
</head>
<body>
<div class="main">
    <div class="main-content">
        <a href="https://www.gesundheitsmanufaktur.de/marken/nuprevento" target="_blank" rel="nofollow noopener">
            <img src="img/logonuprevento.png" alt="Nuprevento" class="logo">
        </a>
        <div class="btn-link">
            <form action="https://www.gesundheitsmanufaktur.de/marken/nuprevento" method="get">
                <button type="submit" formtarget="_blank">Produkte im Partnershop</button>
            </form>
        </div>
        <p>Die Homepage der NuPrevento GmbH befindet sich in der Überarbeitung.</p>
        <p>
            Schreiben Sie uns bei Fragen oder Anregungen gern eine Mail an:
            <a href="mai&#108;&#116;o&#58;i&#110;%66&#111;&#64;&#110;u&#37;&#55;&#48;re%76&#101;n&#37;74o&#46;co%6&#68;">
            inf&#111;&#64;nupr&#101;ve&#110;to&#46;co&#109;</a>
        </p>
        <p class="content">Besuchen Sie in der Zwischenzeit gern unsere Partnerwebseiten:</p>
        <div class="content">
            <a href="https://www.dr-coy.info/" target="_blank">
                <img src="img/logojohannescoy.png" class="coy-logo" alt="Johannes Coy">
            </a>
        </div>
        <div class="bottom-logos">
            <a href="https://www.tavarlin.com/" target="_blank">
                <img src="img/logotavarlin.png" class="tavarlin-logo" alt="Tavarlin">
            </a>
            <a href="https://www.keto-drink.com/" target="_blank">
                <img src="img/ketodrink.svg" class="keto-logo" width="300" height="300" alt="Keto-Drink">
            </a>
        </div>
    </div>

    <div class="footer-nav">
        <hr>
        <ul class="bottom-nav">
            <li><a href="impressum.html" target="_blank">Impressum</a></li>
            <li><a href="datenschutz.html" target="_blank">Datenschutzerklärung</a></li>
        </ul>
    </div>
</div>
</body>
</html>

I am doing a simple homepage with only HTML and CSS, and I have a problem that it shows too much space underneath that is not coming from any of the divs that I tested.

What could be causing it?

I tried removing the negative top position and adding a display:flex to the main container but it did not help either.