Customise 'From' Address for PHP form with some customisation

Question

I have a website and PHP web email form hosted on Godaddy. Everything is working fine. I have already added my proper custom domain email into the php file. But each time I receive an email via the web form, the From address is

accountname@p3plcpnl0913.prod.phx3.secureserver.net

Is there a way to change it? I would like to make some customisation.

1. Is there a way to customise it in a way that my From email address is the same as what I added into my php? I have tried number of methods from this example. https://www.php.net/manual/en/function.mail.php But I did not have any luck.

2. Can I set the From address dynamically same as the Email that will be entered into the form? How can I achieve this?

3. Currently I have set the Subject to be static. I would like to tweak the subject to be a little dynamic. Example - "Sample Contact Form - Entered Email - Current Date"

Here is my PHP file.

<?php

function validate($type, $data = ''){
    $valid = true;

    if(empty($data)){
        $valid = false;
    }

    switch($type){
        case 'email':
            $valid = filter_var($data, FILTER_VALIDATE_EMAIL);
        break;
        case 'telephone':
            $valid = (strlen($data) >= 10);
        break;
        case 'captcha':
            $valid = ($data == 27);
        break;
    }

    return $valid;
}

if($_SERVER['REQUEST_METHOD'] == 'POST' && ($_GET['nonce'] + 22 == 9022)){

    $errors = array();

    $sendTo = array(
        'info@mydomain.com',
    );

        $subject = 'Sample Contact Form';

        $firstname = strip_tags($_POST['firstname']);
        $secondname = strip_tags($_POST['secondname']);
        $email = strip_tags($_POST['email']);
        $captcha = strip_tags($_POST['captcha']);
        $message = strip_tags($_POST['message']);

        if(!validate('text', $firstname)){
            $errors['firstname'] = 'First name is not entered correct';
        }

        if(!validate('text', $secondname)){
            $errors['secondname'] = 'Last name is not entered correct';
        }

        if(!validate('email', $email)){
            $errors['email'] = 'Email address is not entered correct';
        }

        if(!validate('captcha', $captcha)){
            $errors['captcha'] = 'Captcha is not entered correct';
        }

        if(!validate('text', $message)){
            $errors['message'] = 'Message is not entered correct';
        }

        if(!empty($errors)){

            http_response_code(400);
            echo json_encode($errors);
            exit;

        }

        $email_content = "First Name: $firstname\n";
        $email_content .= "Last Name: $secondname\n";
        $email_content .= "Email: $email\n";
        $email_content .= "Message: $message\n";

        if (mail($sendTo[0], $subject, $email_content)) {

            http_response_code(200);
            echo "Message Received";

        } else {

            $errors[] = 'Unable to send request.';
            http_response_code(500);
            echo json_encode($errors);

        }

}else{
    http_response_code(403);
    echo "Error";
}

Would really appreciate if any PHP experts provide a helping hand. Thank you!

Edit 1

But I have checked my Godaddy Settings on cPanel. They seems to be fine. I feel it has to do with my PHP. I am also using Google Workspace for my email.

After attempting several time. I some what manage to change the From address base on the code below. The result I got was,

sendermail@senderdomain via p3plcpnl0913.prod.phx3.secureserver.net 

I followed this example. PHP mail function 'from' address

 $from = $_POST['email'];

(mail($sendTo[0], $subject, $email_content, "From:" . $from))

Now I am facing a new problem. Gmail is marking the email as SPAM.

How can I solve this? Please advice.