adding logo to navbar bootstrap code example

Example 1: bootstrap 4 navbar with logo and nav on right

<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <a class="navbar-brand" href="#">Navbar</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>
  <div class="collapse navbar-collapse" id="navbarNav">
    <ul class="nav navbar-nav ml-auto">
      <li class="nav-item active">
        <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Features</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Pricing</a>
      </li>
      <li class="nav-item">
        <a class="nav-link disabled" href="#">Disabled</a>
      </li>
    </ul>

Example 2: bootstrap navbar logo center

Try this:

.navbar {
    position: relative;
}
.brand {
    position: absolute;
    left: 50%;
    margin-left: -50px !important;  /* 50% of your logo width */
    display: block;
}
Centering your logo by 50% and minus half of your logo width so that it won't have problem when zooming in and out.