Revamp Existing App Functionality

I need an experienced app developer to step into my current code-base and refine several key features so the app feels more polished and reliable. The user interface is already set; your focus will be on functionality—specifically updating and improving parts that are already there rather than adding brand-new modules.

Here’s what I’m after:
• Review the current implementation of the targeted features, identify bottlenecks or logic gaps, and propose concrete improvements.
• Rewrite or adjust the affected modules so they work seamlessly with the rest of the app and its APIs.
• Run thorough unit and integration tests, then deliver a build I can test myself.
• Document the updated code clearly so future maintenance is straightforward.

I’ll give you full access to the repository, a list of the features that need attention, and expected behaviours for each one. Please be comfortable working with version control and providing incremental updates so I can track progress.

If you’ve successfully repaired or enhanced existing apps before—especially where careful refactoring was required—let me know what stack you’ve worked with and share a link or two to comparable projects.