Edit in JSFiddle

var json = {
  questions: [{
    type: "radiogroup",
    hasOther: true,
    isRequired: true,
    name: "favoritePet",
    title: {
      default: "What is your favorite pet?",
      de: "Was ist dein Lieblingshaustier?"
    },
    choices: [{
      value: "dog",
      text: {
        default: "Dog",
        de: "Hund"
      }
    }, {
      value: "cat",
      text: {
        default: "Cat",
        de: "Katze"
      }
    }, {
      value: "parrot",
      text: {
        default: "Parrot",
        de: "Papagei"
      }
    }],
  }],
  completedHtml: {
    default: "Your favorite pet is <b>{favoritePet}</b>.",
    de: "Ihr Lieblingstier ist <b>{favoritePet}</b>."
  }
}

Survey.defaultBootstrapCss.navigationButton = "btn btn-green";
Survey.Survey.cssType = "bootstrap";

window.survey = new Survey.Model(json);

survey.onComplete.add(function(result) {
  document.querySelector('#result').innerHTML = "result: " + JSON.stringify(result.data);
});



$("#surveyElement").Survey({
  model: survey
});
<select onchange="survey.locale = this.value; survey.render();">
    <option value="en" selected=selected>English localization</option>
    <option value="de">German localization</option>
 <select>

<div id="surveyElement"></div>

<div id="result"></div>
select {
  margin-top: 30px;
}

.btn-green {
  background-color: #1ab394;
  color: #fff;
  border-radius: 3px;
  
  &:hover, &:focus {
    background-color: #18a689;
    color: #fff;
  }
}

.panel-footer {
    text-align: right;
    background-color: #fff;
}