There are numerious stories when people get cheated while trading cryptocurrency privately with others or ripped off when shopping online with cryptocurrency. Payment with cryptocurrency is really cool and it is the future of the decentralzied world, especially with the appearance of many stable coins such as USDT, USDC, DAI, which make cryptocurrency payment a realistic choice. However, we need safety and security while doing shopping or trading in the decentralzied world, just as we are doing in the traditional way.
In the centralized world, there are Alipay and Paypal which serve the purpose of arbitration between buyers and sellers originally, however, firstly, they do not support cryptocurrency, secondly, they can only work as arbitrators in their own systems, Taobao and ebay, they cannot guarrantee a safe and secure payment beyond their domain.
For more details:
I used solidity to build smart contract based on Ethereum, working on metamask of Ethereum blockchain and python to interact with contract.
Truffle framework is ledged to compile, deploy and debug smart contract to ropsten and ganache. Mocha test framework is also used for test purpose.
I tried to learn react/redux to make a demo UI which I am not excel at, but I did it in a week.