how to fix mobile layout issue

Add max-width: 100% to .container:

.container {
    border-radius: 10px;
    background-color: #0811202d;
    text-align: center;
    margin: auto;
    padding-bottom: 10px;
    width: 400px;

    max-width: 100%; /*add this it*/
}

And remove width: 400px from .row:

.row {
    border-top-right-radius: 10px;
    border-top-left-radius: 10px;
    height: 90px;

    /*width: 400px;*/ /*remove this it*/

    background-color: #D03737;
    color: #fff;
    font-family: Verdana, Geneva, Tahoma, sans-serif;
}