Excel not working properly since updating to Windows 11

Santero10 After being nagged by Microsoft for a couple of years and now being threatened that unless I upgrade from Windows 10 to Windows 11 soon, my computer will turn into a pumpkin (or some other dire consequence), I finally took the leap thinking that by now, maybe they've worked out the kinks. Nope.

Over the years, I've built what I think is a fairly complicated spreadsheet with a bunch of different worksheets, graphs and pivot tables. I use it every single day. After I updated to Windows 11, it started flaking out occasionally ("not responding", greyed out screen), primarily when I tried to undo something I entered. As time goes on, it's doing this more and more frequently and now it's pretty much to the point where feel like I need to save every 30 seconds lest I lose my work. Sometimes, if I wait for about 5 or 10 minutes, it comes back to life, but lately, it's not been even doing that and my only choice is to kill it from the Task Manager. When I reopen Excel, it sometimes recovers some of my lost edits, but the last few days, it's not even been doing that.

Has anyone come up with a solution for this problem? I'm so frustrated. It's almost unusable at this point (saving every 30 seconds, waiting 5 or 10+ minutes for the software to become responsive again each time this happens ... which seems more and more frequent as time passes). I'm using Office 2019. If I upgrade, will these problems go away? Will my complicated Office 2019 spreadsheet transfer seamlessly to a newer version?

I read up about rolling my system back to Windows 10, but then learned that you can't do that after 30 days (argh!!!). So apparently, I'm SOL there.