I'm not sure I understand. The first person you lost your funds to was supposed to help you recover your funds from your wallet? or was he a scammer and you're now trying to find someone to get you your money back from him?
OP lost $600 to a scammer. Then contacted another scammer who promised to help recover his money from the scammers for a upfront payment of $300. In total OP has lost $900.
OP your money is long gone. No one can help you recover your money back. How would they do that? They would need the private keys to the scammers wallet. If the scammer bitcoin addressed is connected to a centralized exchange you can report to the authorities and ask them to file a complaint to the exchange. Even with that, there is little chance of success