A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
If the problem is that you can't get Excel to run, please do the following.
Verify your startup volume: How to repair a Mac disk with Disk Utility -
Then download a copy of the current version of AutoUpdate from this link, install and then run AutoUpdate to bring your installation to current update level, then restart your Mac. If the updater does not open automatically after download, double-click the downloaded .pkg file. Click this link to download the updater. The update is free.
https://go.microsoft.com/fwlink/p/?linkid=830196
If you still are having an issue, then reinstall Mac OS: How to reinstall macOS - Apple Support