<section class="container">

  <section class="row nav-container">
    <section class="six columns">
      <ul>
        <li><img class="red-star" src="{{site.baseurl}}/img/red-star.svg" alt="Roter Stern"></li>
        <li><a href="{{site.baseurl}}{% if page.lang == "en" %}/en{% endif %}/#info">INFO</a></li>

        {% assign pages=site.pages | where:"ref", page.ref | sort: 'lang' %}
        {% for p in pages %}
          <li class="lang">
            <a href="{{p.url}}" {% if p.lang == page.lang %}class="lang-current"{% endif %}>{{p.lang}}</a>
          </li>
        {% endfor %}

      </ul>
    </section>

    <section class="six columns">
      {% include nav.html navclass="nav-large-screens" %}
    </section>
  </section>

</section>

<section class="container">

  <section class="row nav-container">
    <section class="six columns">
      <ul>
        <li><img class="red-star" src="{{site.baseurl}}/img/red-star.svg" alt="Roter Stern"></li>
        <li><a href="{{site.baseurl}}{% if page.lang == "en" %}/en{% endif %}/#info">INFO</a></li>

        {% assign pages=site.pages | where:"ref", page.ref | sort: 'lang' %}
        {% for p in pages %}
          <li class="lang">
            <a href="{{site.baseurl}}{{p.url}}" {% if p.lang == page.lang %}class="lang-current"{% endif %}>{{p.lang}}</a>
          </li>
        {% endfor %}

      </ul>
    </section>

    <section class="six columns">
      {% include nav.html navclass="nav-large-screens" %}
    </section>
  </section>

</section>

Test site.baseurl for english version
Test site.baseurl for english version
