getting error in form submission

i’m submmit the custom form plugin in a template wordpress page
basically givin the insert query in the page and giving form action in this page
i’m getting 404 error
how to solve it

<?php
// if using a custom function, you need this
global $wpdb

$name = 'name';
$age = 'age';
$email = 'email';
$wpdb->insert( 'customplugin', array( 'name' => $name, 'age' => $age, 'email' => $email ), array( '%s', '%d', '%s' ) )

?>

and form action is the link of the submit page

<form method="post" action="https://localhost/wordpress/formsubmitttt/">

please help me i’m new to wordpress