Delete previous versions before updating? Problems

I have version and on my computor. Want to update to e.e.3. fresh. Should I delete these previous versions before updating? When I tried to delete it failed, because " only the Administrator can do this". I am the owner of this home computer and sole user. How do I do this?
Normally when updating, is it necessary to delete previous versions first?
I ran ESET antivirus and several threats was found with Libri Office identifications. That is why I want to delete the previous versions and reinstall a new version. Many was placed under quarentine by ESET
Libri Office is currently extremely slow when I operate it. That is why I am asking these questions.

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