Capture data with Google People API

Cordial greeting I want to be able to capture data such as the basics (name, surname, email ...) and more specific ones such as the birthday and gender; this through a login button. All good with the basic data (I put code below). But I do not know how to capture the birth date and gender data. Inquiring I stumbled upon what I can do with the Google People API. But I'm new to APIs and I really can not understand how to capture variables by this means.

With this I have been able to capture the basic data

<script src="https://apis.google.com/js/api:client.js"></script>
  <script>
  var googleUser = {};
  var startApp = function() {
    gapi.load('auth2', function(){
      // Retrieve the singleton for the GoogleAuth library and set up the client.
      auth2 = gapi.auth2.init({
        client_id: 'xxx.apps.googleusercontent.com',
        cookiepolicy: 'single_host_origin',
        // Request scopes in addition to 'profile' and 'email'
        scope: 'https://www.googleapis.com/auth/user.birthday.read'
      });
      attachSignin(document.getElementById('customBtn'));
    });
  };

  function attachSignin(element) {
    console.log(element.id);
    auth2.attachClickHandler(element, {},
        function(googleUser) {
          var profile = googleUser.getBasicProfile();
          document.getElementById('name').innerText = "Signed in: " +
              profile.getName();
        }, function(error) {
          alert(JSON.stringify(error, undefined, 2));
        });
  }
  </script>