There are 2 methods to fix this.
Method 1:
Try adding left: 0px; to the .navbar selector.
Here is your code:
.navbar {
  width: 100%;
  background-color: #555;
  overflow: hidden;
  position: fixed;
  top: 0;
  padding: 0px;
  left: 0px;
  scroll-behavior: smooth;
}
.navbar a {
  float: left;
  text-align: center;
  padding: 12px;
  color: white;
  text-decoration: none;
  font-size: 17px;
}
.navbar a:hover {
  background-color: #000;
}
.active {
  background-color: #4CAF50;
}
@media screen and (max-width: 600px) {
  .navbar a {
    float: none;
    display: block;
  }
}
<div class="navbar">
   <a class="active" href="#about">About Me</a>
   <a href="#skills">Skills</a>
   <a href="#schedule">Schedule</a>
   <a href="#contact">Contact</a>
</div>
 
 
Here is a living demo: https://codepen.io/marchmello/pen/gOarVVo
Method 2:
Add margin: 0; to the body selector.
Here is your code:
body {
   margin: 0;
}
    
.navbar {
    width: 100%;
    background-color: #555;
    overflow: hidden;
    position: fixed;
    top: 0;
    padding: 0px;
    scroll-behavior: smooth;
}
.navbar a {
    float: left;
    text-align: center;
    padding: 12px;
    color: white;
    text-decoration: none;
    font-size: 17px;
}
.navbar a:hover {
    background-color: #000;
}
.active {
    background-color: #4CAF50;
}
@media screen and (max-width: 600px) {
    .navbar a {
      float: none;
      display: block;
    }
}
<div class="navbar">
  <a class="active" href="#about">About Me</a>
  <a href="#skills">Skills</a>
  <a href="#schedule">Schedule</a>
  <a href="#contact">Contact</a>
</div>
 
 
Here is a living demo: https://codepen.io/marchmello/pen/KKdMPKJ