Navgation elements disappear when resizing - html

Question

If I put the browser on half screen (windows button + left or right) the top menu items are unreadable and also if I zoom in the top menu are not visible.
Please below html and Css code I guess which is having issue
<div><nav class="navbar-inverse" ng-class="::{'navbar':!isViewNative, 'is-native': isViewNative}"
role="navigation">
<div ng-show="::!isViewNative" class="navbar-header">
<a class="navbar-brand" ng-if="::!portal.logo" href="?id={{::portal.homepage_dv}}"><span>{{::portal.title}}</span></a>
<a class="navbar-brand navbar-brand-logo" ng-if="::portal.logo" href="?id={{::portal.homepage_dv}}">
<img ng-src="{{::portal.logo}}" />
</a>
<button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#sp-nav-bar">
<span class="sr-only">${Toggle navigation}</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
</div>
<div sp-navbar-toggle="" class="collapse navbar-collapse navbar-right" id="sp-nav-bar">
<!-- Include The Menu -->
<sp-widget widget="data.menu"></sp-widget>
<ul ng-if="::(!user.logged_in && page.id != portal.login_page_dv && !data.hasLogin)" class="nav navbar-nav">
<li><a href ng-click="openLogin()">${Login}</a></li>
</ul>
<ul ng-if="::user.logged_in" class="nav navbar-nav">
<!-- chat, avatar, and logout -->
<li class="dropdown hidden-xs">
<a href="javascript:void(0)" class="dropdown-toggle" data-toggle="dropdown">
<span class="visible-lg-inline">${Useful Links}</span>
</a>
<ul class="dropdown-menu">
<li><a ng-href="?id=ess_page_vtb">${Visual Task Boards}</a></li>
<li><a ng-href="?id=reports">${Reports}</a></li>
<li>${Support Portal}</li>
</ul>
</li>
<li ng-if="::data.connect_support_queue_id"><a href ng-click="openPopUp()">${Live Chat}</a></li>
<li><sp-widget widget="data.languageSelector"></sp-widget></li>
<li class="dropdown hidden-xs">
<a href="javascript:void(0)" class="dropdown-toggle" data-toggle="dropdown">
<span class="navbar-avatar"><sn-avatar class="avatar-small-medium" primary="userID" /></span>
<span class="visible-lg-inline">{{::user.name}}</span>
</a>
<ul class="dropdown-menu">
<li><a ng-href="?id=user_profile&sys_id={{::user.sys_id}}">${Profile}</a></li>
<li>${Logout}</li>
</ul>
</li>
<li class="visible-xs-block"><a ng-href="?id=user_profile&sys_id={{::user.sys_id}}"><span class="navbar-avatar"><sn-avatar class="avatar-small-medium" primary="userID" /></span>{{::user.name}}</a></li>
<li class="visible-xs-block">${Logout}</li>
</ul>
</div>
enter code here