Crypto and fiat wallet, crypto exchange app.

I need a developer that's great with editing open source codes and integration of API .. Somebody that's quick and know what's they doing. I'm looking to get a crypto wallets, fiat wallet, send and receive crypto. I will provide the open source files to edit and the API I want to work with. Need IOS and Android app... NO Initial Release Payment.. have to complete mile stone before payment release....