Xamarin and iOS(Swift) developer needed for Mobile App changes

A startup business with social network application having Web and Mobile App channels, is about to be launched. The web version has been updated and now I need to have the App changes in synch with the web version. The developer to create the API and back end web side is in place and standby. I nee someone who will oversee both android and iOS versions. This project should not exceed 3 weeks to complete.