Sorting navigation elements based on tracking data

We have a huge site where the order of the main navigation is not reflected by the usage of these.

e.g.:

Current: Category 1 , Category 2, Category 3.

Category 3 is by far -14:1- the most accessed category, while category 1 is the least accessed. We are proposing reordering these categories so that they reflect the most common usages.

Proposed: Category 3 , Category 2, Category 1.

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Similar to this, each category is actually a dropdown with other categories.

  1. Should we rearrange these categories based on most common uses? (they don't follow any logical sorting at the current time)

  2. If we are using data to sort these categories, how often should we update the navigation?

  3. If a new subcategory is inserted, should this be added to the end of the list?

  4. Is there any negative side of reordering elements in the navigation like users feeling super confused?