JSFiddle - React, Tailwind, and code Playground

HTML

<div class='container'> <!-- parent -->
    <div class='left'> <!-- resizable -->
        <div>
            <div>Account info</div>
            <div>1234567890</div>
        </div>
        <div>
            <div>Client info</div>
            <div>Mr. Nobody</div>
            <div>Birthday: 11/11/1111</div>
        </div>
        <div>
            <div>Warns</div>
            <div>first warning</div>
            <div>secound warning</div>
        </div>
    </div>
    <div class='right'> <!-- fit parent -->
        <table>
            <tr><td>one</td></tr>
            <tr><td>two</td></tr>
            <tr><td>three</td></tr>
            <tr><td>four</td></tr>
            <tr><td>five</td></tr>
            <tr><td>six</td></tr>
            <tr><td>seven</td></tr>
            <tr><td>eight</td></tr>
            <tr><td>nine</td></tr>
        </table>
    </div>
</div>

CSS

.container {
    background-color: gray;
    display: table;
    width: 70%;
    position:relative;
}

.container .left{
    background-color: tomato;
    width: 35%;
}

.container .right{
    position:absolute;
    top:0px;
    left:35%;
    background-color: orange;
    width: 65%;
    height:100%;
    overflow-y: auto;
}

table{ width: 100% }

table td{
    border-spacing: 2px;
    background-color: gray;
}