.nav-tabs,
.nav-pills {
  
  li a:hover {
    color: $white;
  }
}

.nav-tabs {
  margin-bottom: 20px;
}

.nav-tabs,
.nav-pills {
  
  li a:hover {
    color: $white;
  }
}

.nav-tabs {
  margin-bottom: $navbar-margin-bottom;
}

Use -margin-bottom instead of 20px
Use -margin-bottom instead of 20px
