Need to condense data from 60+ Excel sheets into a clear PowerPoint presentation

I am working with an Excel file that has 60+ sheets, each containing different but related data. The expectation is to condense all of this into a ppt for stakeholders.

The main challenge is deciding what to keep, what to summarise, and how to structure the story without overwhelming the slides or disturbing the original Excel file.

For those who’ve handled something similar, how do you usually approach this? Do you start by defining key takeaways, aggregating data first, or building the slide structure upfront? Also, I want to know if there are any services that can help convert complex Excel data into a PPT without hampering the original file? I am sceptical of using a AI tools like ChatGPT because I don’t want to share a confidential file with such tools.