Improve and Stabilise Existing PosterForge Web Application

I am looking for an experienced developer to take over and improve an existing working web application called PosterForge.

The project already has its main functionality implemented. I am not looking for a rebuild from scratch.

The goal of this project is to:

clean up the existing UI/UX so the application is simpler, clearer and easier to use;
review and test the functionality that has already been implemented;
identify bugs, unreliable behaviour or poorly implemented features;
correct and improve those areas where necessary;
tidy the existing code where appropriate;
ensure the main workflows work consistently and reliably.

When the project is returned to me, I want the functionality that has already been started to work properly and reliably, with a much cleaner and easier-to-use interface.

The successful freelancer will be provided with the current complete project to review.

I would prefer somebody who is comfortable working with and improving an existing codebase rather than automatically rebuilding everything.

Further development and additional features may be available as separate work after this initial improvement project is successfully completed.

Please include your experience with taking over existing projects, debugging/improving existing functionality, and UI/UX improvements when submitting your proposal.