.myContent {
    display: flex;
    flex-wrap: wrap;
}

.myContent,
.myMainContent,
.mySection{
    max-width: 100%;
}

.mySection {
    border-bottom: 1px solid #ddd;
}

.mySection:last-child {
    border-bottom: none;
}

h1,h2 {
    margin: 0 0 20px;
}

h1 {
    font-size: 20px;
}

h2 {
    font-size: 18px;
}

@media screen and (min-width: 768px){
    .mySidebar {
        height: 100vh;
        width: 300px;
        background: #ddd;
        border-left: 1px solid #ccc;
        padding: 100px 50px;
        position: fixed;
        right: 0;
        top: 0;
    }

    h1 {
        font-size: 30px;
    }

    h2 {
        font-size: 20px;
    }

    .mySidebar li {
        font-size: 18px;
        margin: 0 0 20px;
    }

    .myMainContent {
        width: calc(100% - 300px);
    }
}