JSFiddle - React, Tailwind, and code Playground

HTML

<link href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap-glyphicons.css" rel="stylesheet">

<div class="accordion-bral">

 <div>
   <!-- accordion item 1 -- start -->
   <input class="ac-input" id="ac-1" name="accordion-1" type="checkbox" checked/>
   <label class="ac-label" for="ac-1">HTML and CSS only<i></i></label>
   <div class="article ac-content">
     <h1 style="position: absolute; margin-left:10px;color:#b70000;">HOUTSOORT</h1>

<div class="flex-container">
     <div class="card">
       <img src="maxopdracht2/eiken-vloer.jpg" style="width:100%">
       <div>
         <input id="checkbox-1" class="checkbox-custom" style="" name="checkbox-1" type="checkbox">
         <label for="checkbox-1" class="checkbox-custom-label">Eiken</label>
       </div>
     </div>
     <div class="card">
     <img src="maxopdracht2/beuken-vloer.jpg" style="width:100%">
     <div>
       <input id="checkbox-1" class="checkbox-custom" style="" name="checkbox-1" type="checkbox">
       <label for="checkbox-1" class="checkbox-custom-label">Beuken</label>
     </div>
     </div>
     <div class="card">
     <img src="maxopdracht2/grenen-vloer.jpg" style="width:100%">
     <div>
       <input id="checkbox-1" class="checkbox-custom" style="" name="checkbox-1" type="checkbox">
       <label for="checkbox-1" class="checkbox-custom-label">Grenen</label>
     </div>
     </div>
     <div class="card">
     <img src="maxopdracht2/maple-vloer.jpg" style="width:100%">
     <div>
       <input id="checkbox-1" class="checkbox-custom" style="" name="checkbox-1" type="checkbox">
       <label for="checkbox-1" class="checkbox-custom-label">Maple</label>
     </div>
     </div>
     <div class="card">
     <img src="maxopdracht2/merbau-vloer.jpg" style="width:100%">
     <div>
       <input id="checkbox-1" class="checkbox-custom" style="" name="checkbox-1" type="checkbox">
       <label for="checkbox-1" class="checkbox-custom-label">Merbau</label>
     </div>
     </div>
     <div...

CSS

.accordion-bral {
  min-height: 0;
  min-width: 220px;
  width: 100%;
  height: 100%;
  background-color: #FFF;
  margin: 0px!important;
}
.accordion-bral .ac-label {
  font-family: Arial, sans-serif;
  padding: 5px 20px;
  position: relative;
  display: block;
  height: auto;
  cursor: pointer;
  color: #777;
  line-height: 33px;
  font-size: 19px;
  background: #EFEFEF;
  border: 1px solid #CCC;
}
.accordion-bral .ac-label:hover {
  background: #b70000;
  color: white;
}
.accordion-bral input + .ac-label  {
  -webkit-transition: all 0.3s ease-in-out;
  -moz-transition: all 0.3s ease-in-out;
  -o-transition: all 0.3s ease-in-out;
  -ms-transition: all 0.3s ease-in-out;
  transition: all 0.3s ease-in-out;
}
.accordion-bral input:checked + .ac-label,
.accordion-bral input:checked + .ac-label:active {
  background-color: #b70000;
  color: #FFF;
  box-shadow: 0px 0px 0px 1px rgba(155, 155, 155, 0.3), 0px 2px 2px rgba(0, 0, 0, 0.1);
}
.accordion-bral input.ac-input {
  display: none;
}
.accordion-bral .article {
  background: white;
  overflow: hidden;
  height: 20px;
  max-height: auto;
  -webkit-transition: all 0.3s ease-in-out;
  -moz-transition: all 0.3s ease-in-out;
  -o-transition: all 0.3s ease-in-out;
  -ms-transition: all 0.3s ease-in-out;
  transition: all 0.3s ease-in-out;
}
.accordion-bral .article p {
  color: #777;
  line-height: 23px;
  font-size: 14px;
  padding: 20px;
}
.accordion-bral input:checked ~ .article i {
  -webkit-transition: all 0.5s ease-in-out;
  -moz-transition: all 0.5s ease-in-out;
  -o-transition: all 0.5s ease-in-out;
  -ms-transition: all 0.5s ease-in-out;
  transition: all 0.5s ease-in-out;
}
.accordion-bral input:checked ~ .article.ac-content {
  height: auto;
}

.accordion-bral i {
  text-decoration:none;
  margin-top: 16px;
  right: 0;
}
.accordion-bral input:checked ~ .ac-label i:after {
   content: "\e114"
}

.accordion-bral input:not(checked) ~ .ac-label i:after {
   content: "\e080"; 
}
.accordion-bral i:after {
 ...