Hey there Kalisto, thanks for the welcome. By errors, do you mean that some pages are in categories that they shouldn't be in? If that's the case, you would have to go to each individual page that has the incorrect category, and change it. For instance, in this page, the source editor for categories looks like this. As long as the page isn't locked, you should be able to add and remove categories from the incorrectly categorized pages. Let me know if you have any questions.
