Any free version of Microsoft Office is likely to be packed with loads of malware. So, as well as getting an illegal download, you're likely to end up with all sorts of nasties on your computer too.
There are plenty of freebies that are just as good, if not better than, Microsoft Office anyway . . .
Apache OpenOffice is one such alternative, that's used by many millions of people worldwide
https://www.openoffice.org/
but it's possibly getting a little long in the tooth these days.
LibreOffice has been spun off from OpenOffice though and is bang up to date:
https://www.libreoffice.org/
SoftMaker FreeOffice is less well-known but it's still cracking good software:
https://www.freeoffice.com/en/
[I've got all three of the above on my computer]
Another freebie, that consistently gets good reviews in the technical press, is WPS Office:
https://www.wps.com/
With so many high-quality freebies available, there's no need to use Microsoft Office at all.