Как добавить фоновое изображение в слайдер отзывов?

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Я пробовал backgroundurl в стилях, но у меня ничего не получилось.

Что я уже пробовал:

<pre lang="text"><pre> <pre><section class="testimonial text-center">
  <div class="container" >
    <h2 style="color:black">Testimonials</h2>
    <section id="carousel">
      <div class="container">
        <div class="carousel slide" id="fade-carousel" data-ride="carousel" data-interval="3000"> 
          <!-- Carousel indicators --> 
          
          <!-- Carousel items -->
          <div class="carousel-inner">
            <div class="item active">
              <div class="profile-circle" > <img src="https://scontent.fdel8-1.fna.fbcdn.net/v/t1.0-9/27752140_1302436453219651_2830378499643641157_n.jpg?oh=9c31d1ab6a1a4141dd7387a39d39a817&oe=5B36D5FF" alt=""> 
              </div>
              <p>I came here to acquire the shape of my body I had half a year ago. I was quite surprised with a range of services they offered me.Moreover, you can benefit from their group training..<br>
                <span>Ravi Singh </span></p>
            </div>
            <div class="item">
              <div class="profile-circle" > <img src="https://scontent.fdel8-1.fna.fbcdn.net/v/t1.0-9/27752140_1302436453219651_2830378499643641157_n.jpg?oh=9c31d1ab6a1a4141dd7387a39d39a817&oe=5B36D5FF" alt=""> 
              </div>
              <p>I came here to acquire the shape of my body I had half a year ago. I was quite surprised with a range of services they offered me.Moreover, you can benefit from their group training.<br>
                <span>Ravi Singh</span></p>
            </div>
                   <div class="item">
              <div class="profile-circle" > <img src="https://scontent.fdel8-1.fna.fbcdn.net/v/t1.0-9/27752140_1302436453219651_2830378499643641157_n.jpg?oh=9c31d1ab6a1a4141dd7387a39d39a817&oe=5B36D5FF" alt=""> 
              </div>
              <p>I came here to acquire the shape of my body I had half a year ago. I was quite surprised with a range of services they offered me.Moreover, you can benefit from their group training.<br>
                <span>Ravi Singh </span></p>
                  </div>
            
          </div>
          <a data-slide="prev" href="#fade-carousel" class="left carousel-control">‹</a> <a data-slide="next" href="#fade-carousel" class="right carousel-control">›</a> 
        </div>
      </div>
    </section>
  </div>
</section>

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