hi dev, my wallet is synced with latest block and i have mined more 6 hours, but wallet balance is still 0. Could you please advise?

That's trading fee, you can see almost exchanges use this fee (bittrex 0.25%, polo 0.15-0.25%, bianance 0.1%, kucoin 0.02%) it's fee for every transaction, if you sell 1btc of NUKO you have to pay 1*0.2% =  0.002bit