Android App bug fixes and improvements

We have a current Android app that communicates to a backend using PHP and JSON. The app is currently at its 95% of completion but it needs some bug fixes. The app is made of a 5 tab menu, the main tab has 3 internal, interactive and synchronized widgets in charge of showing different kind of data. On of the widgets among its expanded view requires native/core graphic knowledge, GPS feed and maps integration. In another section it is required to plot a series of values in the same way as the widget’s expanded view. We need a developer to repair the app and improve its performance, stability and reliability. The known bugs cause unexpected terminations. The slowest and more critical fragments of the app are the ones in charge of downloading and displaying information.