Very few people need the full power of MS office. If you have a hotmail.com/outlook.com/live.com email address you get a very feature complete version of the Office-suite through your browser. It probably would suite 95% of peoples needs. And all files are saved in Onedrive which is also included. About 5 or so gigabytes I think in the free tier
Then you also can go the route of Google if you have a gmail account. Then you get the full blown google version of office and apart form the stuff being in slightly different places than you are used to, everything will be there. You also get slightly more storage-space in the free tier, 15 gigs.
And if you are hell bent on having a local installation of a free office-suite you can use LibreOffice.org
Or the one I prefer. OnlyOffice https://www.onlyoffice.com/download-desktop.aspx?from=desktop
If you need more space you can by just that for cheap at both Microsoft and Google