index.css

@import url('https://fonts.googleapis.com/css2?family=Bebas+Neue&display=swap');

* {
    box-sizing: border-box;
}

body {
    font-family: Arial, Helvetica, sans-serif;
    padding: 10px;
    background-color: #afadad;
}

.header {
    padding: 30px;
    background-image: linear-gradient(rgb(51, 87, 234), rgb(13, 5, 121));
    text-align: center;
    font-family: Arial, Helvetica, sans-serif;
    border-top-left-radius: 25px;
    border-top-right-radius: 25px;
    color: white;
}

.header h1 {
    font-size: 50px;
}

.topnav {
    overflow: hidden;
    background-color: #333;
    border-bottom-left-radius: 25px;
    border-bottom-right-radius: 25px;
}

.topnav a {
    float: left;
    display: block;
    color: #f2f2f2;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
}

.topnav a:hover {
    background-color: #ddd;
    color: black;
}

.logo img {
    width: 130px;
    height: 130px;
    float: left;
}

.leftcolumn {
    float: left;
    width: 75%;
    border-radius: 25px;
}

.rightcolumn {
    float: left;
    width: 25%;
    padding-left: 20px;
    border-radius: 25px;
}

img {
    width: 100%;
    padding: 20px;
}

.card {
    background-color: white;
    padding: 20px;
    margin-top: 20px;
    border-radius: 25px;
}

.row:after {
    content: "";
    display: table;
    clear: both;
}

.footer {
    padding: 20px;
    text-align: center;
    background-color: #ddd;
    margin-top: 20px;
    border-radius: 25px;
}

@media screen and (max-width: 800px) {

    .leftcolumn,
    .rightcolumn {
        width: 100%;
        padding: 0;
    }
}

@media screen and (max-width: 400px) {
    .topnav a {
        float: none;
        width: 100%;
    }
}