payment plugin page

Hello Team,

I have created a plugin to extend the woocomerce class and make payment. Kindly advise how should I call an existing wordpress page and in which location will be the wordpress page? where should I place the phpseclib directory?

//code to generate signature
			$payload=json_encode($payload);
			$rsa= new \wamp642\www\transportation\wordpress\wp-content\phpseclib\phpseclib\Crypt\RSA();
			$rsa->setHash('sha1');
			$rsa->setMGFHash('sha1');
			$rsa->setEncryptionMode(RSA::ENCRYPTION_OAEP);
			$rsa->setPublicKeyFormat(RSA::PUBLIC_FORMAT_PKCS1);
			$rsa->loadKey($publickey);
			$encryptedPayload=base64_encode($rsa->encrypt($payload));
			$signaturedata="appID&merTradeNo=$merTradeNo$merTradeNo&payload=$encryptedPayload&paymentType=$paymentType";
			$sign=base64_encode(hash_hmac('sha512',$signaturedata,$apiKey,true));
			
			
			//initiate payment
			$response = $moovpay->purchase($appID,$merTradeNo,$encryptedPayload,$paymentType,$sign);
			$fh = fopen(plugin_dir_path(__FILE__).'redirect.php', 'w+');
			fwrite($fh, $response);
			fclose($fh);
		<strong>	$redirect_url = plugin_dir_url(__FILE__).'redirect.php';</strong>
  
			return array(
			'result' => 'success',
			'redirect' => $redirect_url
			);

Thanks,

Roshan