SirCharo on "Custom WooCommerce payment gateway redirection issue"

Hello,
I'm developing a custom payment gateway for WooCommerce to process payments through NetCommerce (a local visa and credit card gateway).
1- Collecting customer information is Working fine
2- Sending the information to the gateway website is Working fine
3- Transactions are being made successfully on the gateway website and they successfully send us a message back with the transaction status if accepted or rejected.
The problem i'm facing is that whenever i receive the message from them i'm having errors changing the order status to "Processing" if the transaction was successful, and an error displaying the message received in the signature whenever the transaction is failing to go through.
The redirection is right i assume since I always get back to checkout whenever i'm done from the payment gateway website with a message saying "Thank you for Shopping".
I'm not sure whats wrong with the final step of the file, i checked many other gateways and i think i did the same.
Does anyone have idea about this issue?
The php file can be found here: http://goldeneagleadv.com/NetCommerce_Gateway.php (Right click + Save target as)
Thank you.