Hi Naomi,

>Also in this case most of the screens are dependent on each other.

This app needs refactoring. Refactoring on this level only works when you keep working on the project for a longer period (months or years) and keep evolving it. If your job is to just do some fixes as quickly as possible, refactoring is out of question.

If you only have limited time and there's active no development on this app except for a few "quick" bug fixes, then you can only patch the application. You might be able to fix these bugs, you might introduce new ones... I'd spell this out to the customer and minimize any liability for the result.