React Native App Performance Polish

My cross-platform React Native app is already live on both the App Store and Google Play, but I’d like to give it a final layer of polish. I’m looking for someone who has shipped production apps before and can jump straight into an existing code-base... (Budget: $7 - $8 USD, Jobs: Android, Git, Ionic Framework, iOS Development, Mobile App Development, PhoneGap, React Native, Xcode)