For many years now there's been viable alternatives to the expensive Microsoft Office. OpenOffice is probably the best know, but a fork of that LibreOffice has also gained much ground. The issue today is that LibreOffice is very slow and almost unusable even on fast Mac's.

Having looked at some of the code its not clear why its so laggy, but it was only a quick look. OpenOffice however, which is notably half the size of LibreOffice works just fine so the current recommendation is to uninstall LibreOffice and install OpenOffice which is 100% compatible with all your files.