title: How to close a PopUp which appears through a NavigationController
body: <p>I am creating an app for iOS using xCode with Swift 4.2.
  I have this PopUp which gives information about different topics and links to different websites.</p>
  
  <p>The reason why I embedded a navigation controller is that if I manually add a "back" button the whole webview in my main viewcontroller I'm using reloads and that takes much time.</p>
  
  <p>Anyhow, I want this PopUp to get closed. And I do not find any useful information on the internet about that.
  It would be a great help if you could tell me how I close this popup by simply adding a "X" button to close it without reloading my webview.</p>