Hero section video overflowing (CSS/React)

Question

How do you make a navbar and hero section that fills the height of the screen, and not scrollable?

Currently I am trying:

My nav css:

.NavStyle {
  top: 0;
  width: 100%;
  position: absolute;
  padding-left: 20px;
}

My Hero Section css:

.video-hero {
    object-fit: cover;
    width: 100%;
    height: 100%;
    position: fixed;
    z-index: -1;
  }
  
  .hero-container {
    color: aliceblue;
    width: 100%;
    height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    box-shadow: inset 0 0 0 1000px rgba(0, 0, 0, 0.2);
    object-fit: contain;
  }

My App.js (note my app.css does not have any css):

<div className="App">
      <MyNav />
      <Hero />

      <div className='project-container'>
        Hello-Test
      </div>
      
    </div>

The issue is that the nav bar and hero section DO take the full height..but when I scroll down, the video is sort of repeating and flowing onto the "project-container"?