Add following code to your contoller after checking you've recieved response.

$resultRedirect = $this->resultRedirectFactory->create();
    $resultRedirect->setPath('checkout/onepage/successs');
    return $resultRedirect;

Note that you can directly access resultRedirectFactory, you don't need to inject it.

Add following code to your contoller after checking you've recieved response.

$resultRedirect = $this->resultRedirectFactory->create();
    $resultRedirect->setPath('checkout/onepage/successs');
    return $resultRedirect;

Note that you can directly use resultRedirectFactory, you don't need to inject it.