Sudden strange behavior in all office software:

Word files open up in different fonts (Chinese, Himalaya, etc) instead of the Times New Roman I usually use; numbering/bulletpoints no longer apparent in documents, random codes appearing in them; Powerpoint not able to open my files.... What happened? This happened suddenly and with no obvious reason, but now each time I open my word files I can't predict what font it will choose and reapply on my files... seems to be something affecting all of Office programs, and nothing's wrong with my other computer software.
Was there a recent Office update that might have caused this?
When I try to open "Styles" to see what's going on, that functionality of Word no longer works....
Ran antivirus and nothing apparent.
I hope someone can help me - thanks for reading!

Background on my computer:
I have a Dell that is still running windows 10 because of a Dell problem where updates stopped working, that I haven't solved in the past 2 years, but that is not new...