Collapse

collapse.css

  button.btn.collapsed:before {
    content:'Lees verder' ;
  }

  button.btn:before {
    content:'Sluit' ;
  }

collapse.html

<div class="container">
	<div class="row">
    	<div class="col-md-6">
        
            <p class="intro">This sentence is always visible</p>
            
            <div id="demo" class="collapse">
              	<p class="body">
					This content is collapsible
				</p>
            </div>
            
            <button type="button" class="btn collapsed" data-toggle="collapse" data-target="#demo" aria-expanded="false" aria-controls="collapseExample"></button>
            
        </div><!-- .col -->
      </div><!-- .row -->
    </div><!-- .container -->

functions.php

	// Bootstrap
	wp_enqueue_script( 'bootstrap-cdn-jquery', 'https://code.jquery.com/jquery-3.3.1.slim.min.js' );
	wp_enqueue_script( 'bootstrap-cdn-pop', 'https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js' );
	wp_enqueue_script( 'bootstrap-cdn-js', 'https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js' );
	wp_enqueue_style( 'bootstrap-cdn-css', 'https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css' );