JSFIDDLE
(UPDATED 4/2/2022)
When I click Contact Me link, the jQuery trigger did not SLIDEDOWN to open and SLIDEUP to close the form class="box", but instead it just show and hide instead. Im not sure where I should put the CDN jQuery link in HTML.
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<script>
$(document).ready(function() {
  $("#contactMe").on("click", function() {
    if ($(".box").is(":hidden")) {
      $(".box").slideDown("fast"); 
    } else {
      $(".box").slideUp("fast"); 
    }
  });
});
$(document).ready(function() {
  $(".closebtn").on("click", function() {
    $(".box").slideUp("fast");
  });
});
HEADER IN HTML
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<meta http-equiv="ScreenOrientation" content="autoRotate:disabled">
<meta name="format-detection" content="telephone=no">
<link rel="stylesheet" href="css/main.css">
<link rel="stylesheet" href="css/mediadev.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<title>Resume</title>
</head>
FORM BOX HTML
<div class="box" style="display: none;">
    <div class="info">
      <div class="frm-details">
        <div class="frm-name">LET'S WORK TOGETHER!</div>
        <div class="form-box">
          <div class="frm-header">Let me know what you need!<br> I want to help!</div>
          <div class="frm-error-msg">Please fill in the missing field(s).</div>
          <div class="frm-suc-msg">
            <div class="closebtn">x</div>
            <span class="ty">THANK YOU!</span><br> I will get back to you ASAP!
          </div>
          <div class="frm-group">
            <input name="frm-fname" type="text" id="frm-fname">
            <span class="frm-highlight"></span>
            <span class="frm-bar"></span>
            <label>Full Name:</label>
          </div>
          <div class="frm-group">
            <input name="frm-email" type="email" id="frm-email">
            <span class="frm-highlight"></span>
            <span class="frm-bar"></span>
            <label>Email:</label>
          </div>
          <div class="frm-group">
            <input name="frm-company" type="text" id="frm-company">
            <span class="frm-highlight"></span>
            <span class="frm-bar"></span>
            <label>Company Name:</label>
          </div>
          <div class="frm-group">
            <textarea name="frm-comment" rows="3" id="frm-comment"></textarea>
            <span class="frm-highlight"></span>
            <span class="frm-bar"></span>
            <label>Message:</label>
          </div>
          <div id="mail-status">
            <button type="submit" name="frm-submit" class="btn-submit" onclick="sendContact()">SEND</button>
          </div>
          <!--</form>-->
        </div>
      </div>
    </div>
  </div>
 
    