grav-lecampus/user/themes/lecampus/scss/theme/_header.scss

#header{
  nav{
    @include inlineflex();
    height: 100px;
    & > ul{
      @include inlineflex();
      li{
        margin-left: 10px;
        & > ul{
          display: none;
        }
      }
    }
  }
}