As an accomplished Flutter developer, I possess a proven track record of creating stunning cross-platform mobile applications. My deep understanding of the Dart and Flutter SDK is perfect for resolving the layout, navigation, and visual issues in your app. I've honed my skills in clean software architectures such as MVC, BLOC, and MVVM to ensure efficient and robust code that will enhance your app's performance per your project's needs.
Your needs for addressing server-side errors are also well within my wheelhouse. With solid experience using Firebase, AWS (which includes database management), Django, and NodeJs, I am confident that I can readily handle the API failures, database problems, and authentication issues plaguing your backend.
Moreover, my extensive integration work with various API's including App Payment Gateway integrations strongly aligns with what you need. All my apps, from social media to delivery services clones, have utilized payment gateways and other third-party integrations - features crucial for today's platforms. Additionally, my apps always incorporate push notifications and Analytics which testify to detailed monitoring needed in troubleshooting projects like yours.