MS Office 2011 compatibility with High Sierra and Mojave

Office 2011 is not supported by Microsoft on any version of macOS any more.

There are quite a few known compatibility problems with High Sierra and Mojave. It will not run on Catalina at all.

I second BDAqua and his suggestion for LibreOffice.

I say to at least check it out. I know that I found it capable of satisfying all of my needs. Plus it causes far less problems then MS Office.

Look into the Free LibreOffice...

https://www.libreoffice.org/

Microsoft Office Compatibility with Mojave

This may or may not apply to you... if it does, great, if not, it's an FYI for anyone reading here.

Several years ago, The US Military Exchange opened up online purchasing to all honorably discharged veterans.

MS Office 365 Home (6 licenses) is available through the Exchange at a discount. Several times a year (most notably around the holidays), it goes on sale for $29 for a 1 year subscription. At that price, it's hard to justify purchasing a perpetual license... You can purchase multiple units and stack them up. For the price of a standalone copy of Office 2019, you can get 6 years of Office 365, including a total of 6 TB of OneDrive cloud storage.

Just putting that out there.

Personally, I've tried LibreOffice. I'm not crazy about it, and it's just easier for me to use MS Office, considering how much I have to deal with Office at work.