make resizing layout css

I have a website and want it to resize sort of like this:
anyone know how to do this?
Solution
i'm here trying to help. I said sorry if i false. I got reference from w3school. maybe it can help.
<html lang="en">
    <head>
        <meta charset="utf-8" />
        <title>HTML DOM - Create resizable split views</title>
        <meta name="viewport" content="width=device-width, initial-scale=1" />
        <link rel="stylesheet" href="/css/demo.css" />
        <link rel="preconnect" href="https://fonts.gstatic.com" />
        <link
            rel="stylesheet"
            href="https://fonts.googleapis.com/css2?family=Inter&family=Source+Code+Pro&display=swap"
        />
        <style>
            .container {
                display: flex;

                /* Misc */
                border: 1px solid #cbd5e0;
                height: 16rem;
                width: 100%;
            }
            .container__left {
                /* Initially, the left takes 3/4 width */
                width: 75%;

                /* Misc */
                align-items: center;
                display: flex;
                justify-content: center;
            }
            .resizer {
                background-color: #cbd5e0;
                cursor: ew-resize;
                height: 100%;
                width: 2px;
            }
            .container__right {
                /* Take the remaining width */
                flex: 1;

                /* Misc */
                align-items: center;
                display: flex;
                justify-content: center;
            }
        </style>
    </head>
    <body>
        <div class="container">
            <div class="container__left">Left</div>
            <div class="resizer" id="dragMe"></div>
            <div class="container__right">Right</div>
        </div>

        <script>
            document.addEventListener('DOMContentLoaded', function () {
                // Query the element
                const resizer = document.getElementById('dragMe');
                const leftSide = resizer.previousElementSibling;
                const rightSide = resizer.nextElementSibling;

                // The current position of mouse
                let x = 0;
                let y = 0;
                let leftWidth = 0;

                // Handle the mousedown event
                // that's triggered when user drags the resizer
                const mouseDownHandler = function (e) {
                    // Get the current mouse position
                    x = e.clientX;
                    y = e.clientY;
                    leftWidth = leftSide.getBoundingClientRect().width;

                    // Attach the listeners to `document`
                    document.addEventListener('mousemove', mouseMoveHandler);
                    document.addEventListener('mouseup', mouseUpHandler);
                };

                const mouseMoveHandler = function (e) {
                    // How far the mouse has been moved
                    const dx = e.clientX - x;
                    const dy = e.clientY - y;

                    const newLeftWidth = ((leftWidth + dx) * 100) / resizer.parentNode.getBoundingClientRect().width;
                    leftSide.style.width = `${newLeftWidth}%`;

                    resizer.style.cursor = 'col-resize';
                    document.body.style.cursor = 'col-resize';

                    leftSide.style.userSelect = 'none';
                    leftSide.style.pointerEvents = 'none';

                    rightSide.style.userSelect = 'none';
                    rightSide.style.pointerEvents = 'none';
                };

                const mouseUpHandler = function () {
                    resizer.style.removeProperty('cursor');
                    document.body.style.removeProperty('cursor');

                    leftSide.style.removeProperty('user-select');
                    leftSide.style.removeProperty('pointer-events');

                    rightSide.style.removeProperty('user-select');
                    rightSide.style.removeProperty('pointer-events');

                    // Remove the handlers of `mousemove` and `mouseup`
                    document.removeEventListener('mousemove', mouseMoveHandler);
                    document.removeEventListener('mouseup', mouseUpHandler);
                };

                // Attach the handler
                resizer.addEventListener('mousedown', mouseDownHandler);
            });
        </script>
    </body>
</html>