How i can display a column inline of other columns

i have issue with my design in contact form i am trying to represent my contact form like following picture: https://cdn.discordapp.com/attachments/772606698283073557/951615088966631505/unknown.png

But my columns display vertically and i want the textarea (Message) to be inline with input Subject, could you help me please? Thank you!

My HTML: 

    
<section class="contact-form">
  <div class="container">
  
    <div class="formRow row">
      <div class="titleSection text-center">
        <h2 class="contact_text text-center">Contact Us</h2>
      </div>
      <form action="">

        <div class="col-md-6">

          <div class="form-group">
            <input type="text" class="form-control" placeholder="Subject" required>
          </div>
          <div class="form-group">
            <input type="email" class="form-control" placeholder="Email" required>
          </div>
          <div class="form-group">
            <input type="text" class="form-control" placeholder="Name" required>
          </div>
          

        </div>
        
        <div class="col-md-6 m-0">
          <div class="form-group">
            <textarea name="text" id="" class="form-control" cols="74" rows="3" placeholder="Message"></textarea>
          </div>
        </div>

        <div class="col-md-12 text-center mt-5">
          <div class="contact-btn text-center">
            <input type="sumbit" class="btn" value="Sent Message">
          </div>
        </div>

      
      </form>
      
    </div>
  </div>
</section>

My css:

    /***********************************************
           For Contact Section
************************************************/


.contact-form {
  padding: 56px 0 60px;
}

.formRow{
  display: block;
  flex-wrap: nowrap;
  margin-right: -15px;
  margin-left: -15px;
}

.contact_text{
  color: #990000;
  font-size: 40px;
  font-weight: 700;
}

.titleSection{
  margin-bottom: 30px;
}

.contact-form .form-group .form-control {
    border-radius: 0;
    padding: 20px;
    background: transparent;
    border-color: black;
    min-height: 70px;
    font-size: 16px;
    width: 100%;
    color: black;
}

.contact-form .form-group textarea {
  height: 240px;
}



.btn{
  letter-spacing: 0.1em;
  cursor: pointer;
  font-size: 14px;
  font-weight: 400;
  padding: 0px 0px;
  line-height: 45px;
  max-width: 160px;
  position: relative;
  text-decoration: none;
  text-transform: uppercase;
  width: 100%;
  color:#fff;
  background-color: #990000;
}

>Solution :

You need to encapsulate the columns inside a row

...
<div class="row">
  <div class="col-md-6">
    ...
  </div>
  <div class="col-md-6">
    ...
  </div>
  <div class="col-md-12">
    ...
  </div>
</div>
...

You can check the example below, please note that I have removed the md from the columns classes because the preview is less than the medium screen breakpoint

.contact-form {
  padding: 56px 0 60px;
}

.formRow{
  display: block;
  flex-wrap: nowrap;
  margin-right: -15px;
  margin-left: -15px;
}

.contact_text{
  color: #990000;
  font-size: 40px;
  font-weight: 700;
}

.titleSection{
  margin-bottom: 30px;
}

.contact-form .form-group .form-control {
    border-radius: 0;
    padding: 20px;
    background: transparent;
    border-color: black;
    min-height: 70px;
    font-size: 16px;
    width: 100%;
    color: black;
}

.contact-form .form-group textarea {
  height: 240px;
}



.btn{
  letter-spacing: 0.1em;
  cursor: pointer;
  font-size: 14px;
  font-weight: 400;
  padding: 0px 0px;
  line-height: 45px;
  max-width: 160px;
  position: relative;
  text-decoration: none;
  text-transform: uppercase;
  width: 100%;
  color:#fff;
  background-color: #990000;
}

<link href="https://cdn.jsdelivr.net/npm/bootstrap@4.0.0/dist/css/bootstrap.min.css" rel="stylesheet"/>

<section class="contact-form">
  <div class="container">
  
    <div class="formRow row">
      <div class="titleSection text-center">
        <h2 class="contact_text text-center">Contact Us</h2>
      </div>
      <form action="">
        <div class="row">
        <div class="col-6">
          <div class="form-group">
            <input type="text" class="form-control" placeholder="Subject" required>
          </div>
          <div class="form-group">
            <input type="email" class="form-control" placeholder="Email" required>
          </div>
          <div class="form-group">
            <input type="text" class="form-control" placeholder="Name" required>
          </div>
        </div>
        
        <div class="col-6 m-0">
          <div class="form-group">
            <textarea name="text" id="" class="form-control" cols="74" rows="3" placeholder="Message"></textarea>
          </div>
        </div>

        <div class="col-12 text-center mt-5">
          <div class="contact-btn text-center">
            <input type="sumbit" class="btn" value="Sent Message">
          </div>
        </div>
        </div>

      
      </form>
      
    </div>
  </div>
</section>