@LucaBrocato
Welcome to the forum!
You should be able to go to the Category where you published the Family of the content, Right click on the Family, and simply delete the entire family. But you may also want to simply replace it with the corrected geometry:
Place an instance of the part in an assembly, using the "As Custom" option so that you can make changes to it. Edit the part to make whatever geometry changes you need. Then return to the Family in the Content Center, Right Click and choose Replace Family Template. Usually this will work depending on how many changes you have made.

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Chris Benner
Community Manager