JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box">
            <h1><p>Moderní webdesign</p> za nejnižší ceny!</h1>
         </div>

CSS

html,body
{
    height: 100%;
}

.box{
float: left;
margin: 250px 0 0 0;
height: 35%;
width: 50%;
background-image: url('img/header-bcg.png');
}

.box h1{
font-size: 40px;
font-family: Bree serif;
color: 33adae;
margin-top: 30px;
margin-right: 15px;
line-height: 10px;
float: right;
} 

@media screen and (max-width: 768px) {
    .section1 {
        width: 100%;
    }

    .box{
      width: 100%;
        display: table;
        margin: 0;
        float: none;
        height: 100%;
    }

    .box h1{
      text-align: center;
      margin: 0 auto;
        display: table-cell;
        float: none;
        vertical-align: middle;
    }

    footer, nav{
      width: 100%;
    }
}