Need help with implementing GiveWP custom PG

Hi,

I am a developer and need the GiveWP custom redirection gateway plugin for the site. As I read a support document, it lectures to develop a gateway with paying buy credit card function hosted inside.

https://givewp.com/documentation/developers/how-to-build-a-gateway-add-on-for-givewp/

But my requirement is, after selecting gateway I should be able to redirect to my IPG page (Not hosted inside) and I will process my transaction outside.
After all done, I should be able to return to success page.

I have searched many places for the help but I could not find the single way of developing it.

Please explain me to develop with this.

Thanks