{% assign activities_count = 0 %}
{% for course_section in course.sections %}
  {% for course_activity in course_section.activities %}
    {% assign activities_count = activities_count | plus: 1 %}
  {% endfor %}
{% endfor %} 

<div class="np-course-details">
    <div class="np-course-detail">                 
        <strong>{{ activities_count }}</strong>
        <span class="np-details-label">
          {% if activities_count == 1 %}Activity{% else %}Activities{% endif %}
        </span>
    </div>
    <div class="np-course-detail">
    </div>
    <div class="np-course-detail">
      {% if course.properties.course_length contains 'missing property' %}
        missing property: course.properties.course_length
      {% else %}
        {% if course.properties.course_length %}
          {% if course.properties.course_length > 0 %}
              <strong>{{course.properties.course_length}}</strong> mins
              <span class="np-details-label lang-en">Duration</span>
              <span class="np-details-label lang-es">Duración</span>
          {% else %}
              <div>&nbsp;&nbsp;&nbsp;</div>
          {% endif %}
        {% endif %}
      {% endif %}
    </div>
</div>

<style>
  .np-course-details {
    text-shadow: 1px 1px black;
  }
</style>