Reducing size of the container using bootstrap

Question

Hi Team

I am creating a form from the back end side using php i have cdn libraries, but need to reduce size of the container its big.

// html form

// Create the HTML form
$htmlForm = '<div class="container">
    <div class="card">
        <div class="card-body text-center">
            <form action="://' . $pfHost . '/eng/process" method="post">
                <div class="row justify-content-center">
                    <div class="col-md-6">
                        <div class="mb-3">';
foreach ($data as $name => $value) {
    $htmlForm .= '<input name="' . $name . '" type="hidden" value=\'' . $value . '\' />';
}
$htmlForm .= '<button type="submit" class="btn btn-primary">Pay Now</button></div></div></div></form>
        </div>
    </div>
</div>';

echo $htmlForm;