I have a question so if we want to have an auction system in the marketplace should we have another contract for Auction or should we put it inside the marketplace contract.
And second, is there any point to make a bit in the smart contract other than the balance check or if we do it on the website is it have any disadvantage because right now we have argued about this one in our project. Because the fee is quite high if we have bid on the smart contract which might not pleasant.
hey @Pong88 ! If you want to have an Auction functionality, thats definitely another contract. For each bit, you are right, its a lot of fees in the ethereum mainnet, but its blockchains like poligon or binance smart chain.
Thank you so much for your answer @kenn.eth, and I am a bit confused about the last part. Do you mean for the blockchain such as Polygon and Binance NOT Ethereum mainnet can be less fee, is that correct? 
Yes thats correct, transaction fees in this blockchains are very little. So you can build stuff that require more transactions.