Hello Minaz,

I hope this is what you're looking for,

Custom HTML form:

<form action="https://checkout.TestPay.com/paymentPage" method="POST">
    <input type="text" name="card_number"/>
    <input type="text" name="card_holder_name"/>
    <input type="text" name="expiry_date"/>
    <input type="password" name="card_security_code"/>
    <button value="Send" type="submit"/>
</form>   

*You can add the payment-acquirer page's URL in the form action

*And can submit the form using a controller function and can redirect to any URL 

*Or can submit from js(eg:- form.submit() )

Regards