@media screen and (max-width: 800px) {
    .plan{
        display: none;
    }
    .main-content{
        width: 90%;
        display: flex;
        align-items: center;
    }
    nav{
        display: none;
    }
    body, html{
        font-size: 15px;
    }
    #double{
        flex-flow: column nowrap;
    }
    #double li{
        padding-top: 10px;
    }
    #double-element{
        width: 90%;
    }
    .btn-menu-phone{
        display: flex;
        justify-content: center;
        align-items: center;
        position: fixed;
        bottom: 20px;
        right: 20px;
        z-index: 10;
        width: 60px;
        height: 60px;
        border-radius: 50%;
        background-color: #111;
    }
}
@media screen and (min-width: 800px) {
    .btn-menu-phone{
        display: none;
    }
}