Repair Existing excel Business Workbook/ not a rebuild

I am looking for an experienced Microsoft Excel developer to assess and repair an existing business workbook called LIOS (LiquirigS Intelligent Operating System).

This workbook has been developed over several years and is used daily to run key parts of my business. I am not looking for a new system or a complete rebuild. My objective is to repair and preserve the existing workbook wherever possible.

The workbook appears to function correctly in most areas. However, I believe there is a fault within the sales import process, and I would like an experienced Excel specialist to inspect the workbook and provide an independent assessment.

Before carrying out any work, I would like you to:

* Inspect the workbook.
* Explain whether it is repairable.
* Identify the issues you find.
* Recommend the best solution.
* Provide a fixed-price quotation before making any changes.

If the workbook can be repaired, I would like the existing functionality preserved wherever possible.

Please include in your reply:

* Your experience repairing large Excel workbooks.
* Your experience with VBA, Power Query and advanced Excel formulas.
* Whether you have repaired existing business systems rather than building new ones.
* Your estimated number of hours for the work.

The workbook will only be shared with shortlisted freelancers after an initial discussion due to the confidential nature of the business data.
Please do not quote for a complete rebuild unless, after inspection, you can explain why the existing workbook cannot reasonably be repaired.