Why does a part of the navigation bar disappear when the screen gets smaller

I created a nav bar in React and CSS with the following code:

<header className="home-header">
      <div className="auth-buttons">
         <input type="button" className="auth-button sign-up-button" value="Sign Up" />
         <input type="button" className="auth-button login-button" value="Login" />
     </div>
     <div className="menus-container">
         My Site
         <span></span>
         <span></span>
         <span></span>
    </div>
</header>

and

.home-header {
    position: sticky;
    padding: 1.5rem;
    margin-top: 0;
    min-width: 100vh;
  
    background-color: #1441aa;
    border-bottom-right-radius: 30px;
    box-shadow: 0 3px 10px rgb(0 0 0 / 0.2);
  
    display: flex;
    flex-direction: row;
    justify-content: space-between;
  }

  .home-header .auth-buttons {
    display: flex;
    flex-direction: row;
    gap: 3px;
    /* margin-left: 10%; */
  }

  .home-header .auth-buttons .auth-button {
    padding: 0.5rem 1.5rem;
    border: none;
  }

  .home-header .auth-buttons .auth-button:hover {
    cursor: pointer;
  }

  .home-header .auth-buttons .sign-up-button {
     border-bottom-left-radius: 1rem;
  }

  .home-header .menus-container {
    /* margin-left: 60%; */
    color: #fff;
    font-size: 1.5rem;
    font-weight: 400;
  }

  .home-header .auth-buttons .login-button {
    border-top-right-radius: 1rem;
  }

But when I make the screen smaller, the right part of the navbar disappears, as shown below:

Full Screen:

Smaller Screen:

I want the nav bar to be responsive and get smaller as the screen gets smaller, not disappear. Could you help me?

It's because u set min-width: 100vh; which referts to the window height. You need to change that to vw (viewport width) or use %.

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-css -->

.home-header {
    position: sticky;
    padding: 1.5rem;
    margin-top: 0;
    min-width: 100%; // the difference is this value
  
    background-color: #1441aa;
    border-bottom-right-radius: 30px;
    box-shadow: 0 3px 10px rgb(0 0 0 / 0.2);
  
    display: flex;
    flex-direction: row;
    justify-content: space-between;
  }

  .home-header .auth-buttons {
    display: flex;
    flex-direction: row;
    gap: 3px;
    /* margin-left: 10%; */
  }

  .home-header .auth-buttons .auth-button {
    padding: 0.5rem 1.5rem;
    border: none;
  }

  .home-header .auth-buttons .auth-button:hover {
    cursor: pointer;
  }

  .home-header .auth-buttons .sign-up-button {
     border-bottom-left-radius: 1rem;
  }

  .home-header .menus-container {
    /* margin-left: 60%; */
    color: #fff;
    font-size: 1.5rem;
    font-weight: 400;
  }

  .home-header .auth-buttons .login-button {
    border-top-right-radius: 1rem;
  }

<!-- language: lang-html -->

<header class="home-header">
      <div class="auth-buttons">
         <input type="button" class="auth-button sign-up-button" value="Sign Up" />
         <input type="button" class="auth-button login-button" value="Login" />
     </div>
     <div class="menus-container">
         My Site
         <span></span>
         <span></span>
         <span></span>
    </div>
</header>

<!-- end snippet -->

In the CSS for .home-header, min-width is sized with the vh unit rather than vw, meaning it will scale according to the height of the screen rather than the width.

Change min-width: 100vh; to min-width: 100vw;.

Additionally, your header may get cut off the right side of screen due to its padding. Add the rule box-sizing: border-box; so that it will be sized correctly.