Setting up a feedback form?

Question

PHP

<form>
          <!-- Hidden Required Fields -->
          <input type="hidden" name="project_name" value="Site Name">
          <input type="hidden" name="admin_email" value="[email protected]">
          <input type="hidden" name="form_subject" value="Form Subject">
          <!-- END Hidden Required Fields -->

          <input type="text" name="Name" id="Name" placeholder="You name..." required><br>
          <input type="text" name="E-mail" id="E-mail" placeholder="You E-mail..." required><br>
          <input type="text" name="Phone"   id="Phone" placeholder="You phone..."><br>
          <button>Send</button>
        </form>

.block5 input {
  width: 600px;
  text-align: center;
  margin: 1px;
  border: none;
  background-color: #26292e;
}

.block5 #Name, #E-mail {

  height: 50px;
}

.block5 #Phone {
  height: 500px;
}

$("form").submit(function() { //Change
    var th = $(this);
    $.ajax({
      type: "POST",
      url: "mail.php", //Change
      data: th.serialize()
    }).done(function() {
      alert("Thank you!");
      setTimeout(function() {
        // Done Functions
        th.trigger("reset");
      }, 1000);
    });
    return false;
  });

I took a ready-made feedback form for the landing, but I only have one line of text in the 3rd input field, and I need more. How to do it?
How it is now:
How it should be:

Answer 1

Good afternoon.
In your example, there are three input fields, and you write that one.
To add one or more input fields, add the required number of inputs to the form.
What is the problem?