Assemble Utility App iOS/Android

I have the core screens, assets, frond end, backend code and a clear flow mapped out; now I need someone to pull everything together into fully functioning builds for both iOS and Android. The app is strictly utility-focused, so the experience should stay light, quick to load, and easy to maintain... (Budget: £20 - £250 GBP, Jobs: Android, Android App Development, Flutter, iOS Development, iPhone, Mobile App Development, Mobile Development, Objective C, React Native, Software Development)