index.css

html {
    scroll-behavior: smooth;
}

.flex {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-evenly;
}

body {
    margin: 0px;
    padding: 0px;
    display: grid;
    background-color: white;
    grid-template-columns: 180px 1fr;
    grid-template-rows: auto auto auto auto auto auto;
    font-family: Arial, Helvetica, sans-serif;
}

nav {
    background-color: white;
    left: 0px;
    position: fixed;
    width: 180px;
    height: 100vh;
    box-shadow: 5px 0 5px -7px #333;
    padding: 0px;
}

#whole_nav {
    grid-column: 1/2;
    grid-row: 1/7;
}

a {
    text-decoration: none;
    color: black;
}

.c1 {
    height: 100vh;
    /* background-image: url(picture/logo.png); */
    background-color: rgb(56, 158, 153);
    background-repeat: no-repeat;
    background-size: cover;
    position: relative;
    overflow: hidden;
}

.c1 img {
    display: block;
    margin-left: auto;
    margin-right: auto;
    width: 50%;
}

.overlay {
    background-color: black;
    height: 100%;
    width: 100%;
    opacity: .3;
    position: absolute;
}

.c1 h1 {
    text-align: center;
    color: rgba(255, 255, 255, 0.411);
    z-index: 10;
    position: relative;
}

.c {
    padding: 1rem;
}

nav h1 {
    font-size: 2rem;
    margin: 0px;
    margin-top: 30px;
    color: rgb(56, 158, 153);
}

nav h6 {
    margin-top: 0px;
}

.logo {
    border-bottom: 1.5px solid rgb(56, 158, 153);
    text-align: center;
}

li {
    list-style-type: none;
}

h2 {
    height: auto;
    padding-bottom: 10px;
    color: white;
    background-color: rgb(56, 158, 153);
    height: 50px;
    margin-top: 0px;
    padding-top: 20px;
    padding-left: 10px;
}

h3 {
    color: rgb(56, 158, 153);
}

#mahara {
    width: 100%;
}

#maharaPicture {
    border-bottom: 0.5px solid rgb(190, 190, 190);
}

.card {
    background-color: white;
    width: 25rem;
    margin-bottom: 5rem;
    box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2);
}

.card .cardText {
    padding: 1rem;
}

.projekte .cardPicture {
    background-color: white;
    background-repeat: no-repeat;
    background-size: cover;
    height: auto;
}

.horizontalCard {
    height: 10rem;
    background-color: white;
    width: 70%;
    align-items: center;
    /* min-width: 465px;  */
    margin: 0 auto;
    margin-top: 4rem;
}

.hCardText {
    padding-top: 2.6rem;
}

.hCardText h2 {
    background-color: white;
    color: black;
}

.hCardPicture {
    float: left;
    width: auto;
    height: 60%;
    padding-top: 1.2rem;
    margin-right: 2rem;
    padding-left: 2rem;
}

.hCardPicture img {
    max-height: 100%;
    max-width: 100%;
}

img {
    max-width: 100%;
    max-height: 100%;
}

.button {
    display: block;
    text-decoration: none;
    width: 1fr;
    height: 25px;
    padding: 10px;
    padding-top: 10%;
    text-align: center;
    color: black;
    /* border-bottom: 1px solid black; */
    border-bottom: 0.5px solid rgb(190, 190, 190);
}

.button:hover {
    background-color: rgb(206, 206, 206);
    height: 1fr;
    width: 1fr;
    border-left: 3px solid rgb(56, 158, 153);
    ;
}

/* .button {
    background-color: white;
    color: black;
    border: 2px solid #4CAF50;
    padding: 10px 20px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 16px;
    min-width: 1fr;
} */

p {
    font-size: 1.5rem;
    color: #333333;
    width: 95%;
    margin: 20px;
    line-height: 2.88rem;
}

@media screen and (max-width: 635px) {
    body {
        margin: 0px;
        padding: 0px;
        display: grid;
        background-color: white;
        grid-template-columns: 1fr;
        grid-template-rows: [first]auto auto auto auto auto auto auto;
        font-family: Arial, Helvetica, sans-serif;
    }
    nav {
        display: none;
    }
    #first img {
        width: 100%;
    }
}

@media screen and (max-width : 900px) {
    .horizontalCard {
        height: auto;
        background-color: rgb(56, 158, 153);
        width: 90%;
    }
    .hCardPicture img {
        display: none;
    }
}