Comment créer un formulaire responsive en 2 colonnes avec Contact Form 7 ?

<div id="formulaire-responsive" class="clearfix">

<div class="rang-form">
<div class="demi-colonne">Votre prénom [text* first-name]</div>
<div class="demi-colonne">Votre nom [text* last-name]</div>
</div>

<div class="rang-form">
<div class="demi-colonne">Email [email* your-email]</div>
<div class="demi-colonne">Téléphone [text* your-phone]</div>
</div>

<div class="rang-form">
<div class="colonne">Sujet [text* your-subject]</div>
</div>

<div class="rang-form">
<div class="colonne">Votre message  [textarea your-message]</div>
</div>

<div class="rang-form">
<div class="colonne">[submit "Envoyer"]</div>
</div>

</div><!--fin de formulaire-responsive-->

#formulaire-responsive {
	max-width:600px /*-- à modifier en fonction de la largeur désirée --*/;
	margin:0 auto;
        width:100%;
}
.rang-form {
	width: 100%;
}
.demi-colonne, .colonne {
	float: left;
	position: relative;
	padding: 0.65rem;
	width:100%;
	-webkit-box-sizing: border-box;
        -moz-box-sizing: border-box;
        box-sizing: border-box
}
.clearfix:after {
	content: "";
	display: table;
	clear: both;
}

/**---------------- Media query ----------------**/
@media only screen and (min-width: 48em) { 
	.demi-colonne {
		width: 50%;
	}
}

.wpcf7 input[type="text"], .wpcf7 input[type="email"], .wpcf7 textarea {
	width: 100%;
	padding: 8px;
	border: 1px solid #ccc;
	border-radius: 3px;
	-webkit-box-sizing: border-box;
	 -moz-box-sizing: border-box;
	      box-sizing: border-box
}
.wpcf7 input[type="text"]:focus{
	background: #fff;
}
.wpcf7-submit{
	float: right;
	color: #69af36; 
      font-family: 'Noto Sans', sans-serif;
      border-color: #69af36; 
      font-size: 14px; 
  	  line-height: 49px; 
      height: 49px; 
      font-weight: 600; 
      background-color: #ffffff; 
      border-radius: 4px; 
          -moz-border-radius: 4px; 
          -webkit-border-radius: 4px; 
       text-transform: uppercase; 
       border-width: 2px;  
       padding-left: 26px; 
       padding-right: 26px;
}
.wpcf7-submit:hover{
	background: #69af36;
      color: #ffffff;
  }
span.wpcf7-not-valid-tip{
	text-shadow: none;
	font-size: 12px;
	color: #fff;
	background: #ff0000;
	padding: 5px;
}
div.wpcf7-validation-errors { 
	text-shadow: none;
	border: transparent;
	background: #f9cd00;
	padding: 5px;
	color: #9C6533;
	text-align: center;
	margin: 0;
	font-size: 12px;
}
div.wpcf7-mail-sent-ok{
	text-align: center;
	text-shadow: none;
	padding: 5px;
	font-size: 12px;
	background: #59a80f;
	border-color: #59a80f;
	color: #fff;
	margin: 0;
}