Hi,
Just duplicate the PayPal files in gateways, change the names from PayPal to Molpay, remove those functions that u think it doesn’t needed. Refresh the wordpress webpage once, EMPro will auto create MolPay in database.
Keep on debug and try editing the gateways php files functions. This may give you an idea how to starting on it.
P.S: Duplicate your WordPress site before starting any test & debug. Modify your code at the new duplicated site to prevent any data lost.