PHP - html form sent to gmail account - php

Question

I never used PHP before, but I need to set up an HTML form from to be sent from my website to my gmail account. Checked some tutorials and came up with this code. But for some reason it is not working. When I hit submit it goes to a "Page Not Found
Looks like you've followed a broken link or entered a URL that doesn't exist on this site." Not sure what am I doing wrong.
I have my HTML document, and I have my PHP document. Saved together.
<form action="contact.php" method="POST" name="form">
<div class="row">
<div class="col-12 col-md-6">
<div class="contact-form">
<label for="name">Please enter your name:</label>
<input name="name" type="text" class="form-control" placeholder="Harry Potter">
</div>
</div>
<div class="col-12 col-md-6">
<div class="contact-form">
<label for="mail">Your email address:</label>
<input name="mail" type="email" class="form-control" placeholder="harry#potter.com">
</div>
</div>
</div>
<div class="row">
<div class="col-12">
<div class="contact-form">
<label for="message">How can I help you?</label>
<textarea name="message" class="form-control" id="form-text" cols="30" rows="10" placeholder="Let's do some magic"></textarea>
</div>
</div>
</div>
<div id="submit" class="text-center">
<button name="submit" type="submit" class="btn mt-5 mx-auto">Submit</button>
</div>
</form>
<?php
if(isset($_POST["submit"])) {
$name=$_POST["name"];
$mailFrom=$_POST["mail"];
$message=$_POST["message"];
$mailTo = "myaddress#gmail.com";
$subject = "Form from my website";
$headers = "From: ".$mailFrom;
$txt = "You have received an e-mail from ".$name."\n\n".$message;
if(mail($mailTo, $subject, $txt, $headers)) {
echo "<h1>I recieved your email! Will be in touch with you soon.</h1>";
}
else{
echo "<h1>Something went wrong! Try again.</h1>";
}
header("Location: https://www.whatever.com");
}
?>