解决Flexbox布局中表单宽度超出容器的问题

.columnstest {
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  width: 756px;
  height:500px;
  margin: 0 auto;
}

.columntest h3 {
  color: white;
  font-weight: 30px;
}

.columntest p {
  font-family: 'Roboto', sans-serif;
  color: white;
}

.columntest {
  flex: 1;
}

.bgColor {
  background-color: #C32F4B;
  width: fit-content;
}

.container {
  padding: 12px 24px 24px 24px;
  margin: 48px 12px;
  border-radius: 4px;
  width:200px;
  height:400px;
}

/* Add styles to 'label' selector */

label {
  font-size: 0.85em;
  margin-left: 12px;
}

/* Add styles to 'input' and 'textarea' selectors */

input[type=text], input[type=email], textarea {
  width: 100%;
  padding: 12px;
  border: 1px solid #ccc;
  border-radius: 4px;
  box-sizing: border-box;
  margin-top: 6px;
  margin-bottom: 16px;
  resize: vertical;
}

/* Add styles to show 'focus' of selector */

input[type=text]:focus, input[type=email]:focus, textarea:focus {
  border: 1px solid green;
}

/* Add styles to the submit button */

input[type=submit] {
  background: #C32F4B;
  margin: 0 auto;
  outline: 0;
  color: white;
  border: solid 1px white;
  padding: 12px 24px;
  border-radius: 4px;
  transition: all ease-in-out 0.1s;
  position: relative;
  display: inline-block;
  text-align: center;
}

/* Add styles for 'focus' property */

input[type=submit]:focus {
  background: #A5D6A7;
  color: whitesmoke;
}

/* Style 'hover' property */

input[type=submit]:hover {
  background: #2196F3;
}

/* Align items to center of the 'div' with the class 'center' */
.center {
  text-align: center;
}

/* label color */
label {
  color: white;
}

/* tel part */
input[type=tel], textarea {
  width: 100%;
  padding: 12px;
  border: 1px solid #ccc;
  border-radius: 4px;
  box-sizing: border-box;
  margin-top: 6px;
  margin-bottom: 16px;
  resize: vertical;
}

<div class="bgColor">
  <div class="columnstest">
    <div class="columntest">
      <!--Corporate section(beta testing)-->
      <h3 class="middleh4">Corporate</h3>
      <p>About Us</p>
      <p>Products</p>
      <p>Shop</p>
      <p>Career Opportunity</p>
      <p>Privacy Policy</p>
      <p>Terms Of Servrice(TOS)</p>
      <p>FAQs</p>
    </div>
    <div class="columntest">
      <!--Contact Us Section(beta testing)-->
      <h3 class="middleh4">Contact Us</h3>
      <p><a class="__cf_email__" data-cfemail="046d6a626b44652a697d">[email protected]</a></p>
      <p>a.my</p>
      <p>havvaagrotech</p>
      <h3 class="middleh4">Office</h3>
      <p>Address</p>
    </div>
    <div class="columntest">
      <!--Enquiries Section(beta testing)-->
      <h3 class="middleh3">Enquiries</h3>
      <div class="container">
        <form action="#" name="contact_form">
          <input name="name" type="text" required placeholder="Name"/>
          <input id="telNo" name="telNo" type="tel" placeholder="Telephone Number">
          <input name="email" type="email" required placeholder="Email"/>
          <textarea name="message" cols="30" rows="3" placeholder="Enter your message here ..."></textarea>
          <div class="center">
            <input type="submit" value="Submit">
          </div>
        </form>
      </div>
      <h6>Copyright ©2022 A Agrotech. All Rights Reserved<br>This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.</h6>
    </div>
  </div>
</div>