Improve this with a more flex interface and a better set of colors and fonts and @import to get a google font
<html>
  <head>
    <title>Progressbar95</title>
    <style>
      body {
        background-color: #fff;
        font-family: Arial, sans-serif;
        margin: 0;
        padding: 0;
      }

      #titlebar {
        width: 100%;
        height: 5%;
        background-color: #000;
        color: #fff;
        display: flex;
        justify-content: flex-start;
        align-items: center;
        padding-left: 10px;
      }

      #titlebar img {
        height: 30px;
        margin-right: 10px;
      }

      #my-menu {
        width: 15%;
        background-color: #eeeeee;
        padding: 50px;
      }
      .othersection {
        width: 85%;
        background-color: #a9a9a9;
        padding: 10px;
        overflow: auto;
        scroll: vertical;
      }

      .window {
        width: 60%;
        min-height: 200px;
        background-color: #fff;
        margin: 10px auto;
        padding: 10px;
        border: 1px solid #000;
      }
      .flexelement {
        display: flex;
        flex-direction: row;
        height: 95%;
      }
      .flex2 {
        display: flex;
        flex-direction: column;
        height: 100%;
      }
    </style>
  </head>
  <body>
    <div class="flex2">
      <div id="titlebar">
        <img src="progressbar_computer.jpeg" />
        Progressbar95
      </div>

      <div class="flexelement">
        <div id="my-menu">
          <h3>My Menu</h3>
          <ul>
            <li>CPU: Intel Core i7</li>
            <li>RAM: 16GB</li>
            <li>HDD: 1TB</li>
            <li>GPU: NVIDIA GTX 1660</li>
            <li>FDD: Not Available</li>
          </ul>
        </div>
        <div class="othersection">
          <div class="window">
            <p>Normal</p>
            <p>
              This is the smartest progress bar ever! It is based on B1 AI chip
            </p>
          </div>

          <div class="window">
            <p>Fire!</p>
          </div>

          <div class="window">
            <p>Not now</p>
          </div>

          <div class="window">
            <p>
              Hi! This is a game disk. It changes each time you run Progressbar.
              Each time bonuses and secrets are placed in new location. Find
              them all. Good luck!
            </p>
          </div>

          <div class="window">
            <p>Unlocked</p>
          </div>

          <div class="window">
            <p>Progress points:</p>
            <p>Do you want to be fired?</p>
          </div>

          <div class="window">
            <p>Boo-hoo!</p>
          </div>

          <div class="window">
            <p>Gamepad</p>
          </div>

          <div class="window">
            <p>Unfortunately you are out of the Progress Data</p>
          </div>

          <div class="window">
            <p>We love you!</p>
            <p>
              Progressnet is a hypertextual adventure for curious users. By
              exploring in-game web-pages you can discover cookies, bonuses,
              cheats, easter eggs and other secrets
            </p>
          </div>

          <div class="window">
            <p>Computer:</p>
            <p>Progressbar keyboard</p>
          </div>
        </div>
      </div>
    </div>
  </body>
</html>