nav {
    display: inline-block;
    box-sizing: border-box;
    height: 100%;
    width: 10%;
    background-color: #087a41f8;
    top: 0;
    left: 0;
    position: fixed;
    padding: 0 20px;
}
nav ul {
    list-style: none;
    padding: 0;
}
nav a {
    text-decoration: none;
    color: white;
    display: block;
    padding: 8px;
}
nav a:hover {
    transition: 0.5s;
    color: yellow;
}

main {
    margin-left: 300px;
    padding: 10px;
}

body {
    font-family: Arial, Helvetica, sans-serif;
    font-size: 20px;
    max-width: 90%;
    background-color: white;
    color: black;
}

img {
    padding: 0;
    box-shadow: 5px 5px 5px black;
    max-width: 80%;
}

.container {
    color: black;
}

@media screen and (max-width: 900px){
    nav {
     width: 100%;
     height: 220px;
     padding: 8px 12px;
    }
    main {
     margin-left: 0;
     margin-top: 200px;
    }
    nav ul {
     margin: 0;
    }
    nav li, nav a {
     display: inline-block;
    }
 }