DATABASE FIX

We have had a database built however it needs to be fixed so that it can allow for a many to many relationship between items and the categories within which those items should be included. Right now, each item can only belong to one category. To make the item belong to multiple categories, multiple versions of the same item must be created, each with its own unique ID#. One problem with this arrangement is this: since each item has keywords attached for the search feature, when a keyword is entered if that item has had duplicates created in order to be able to assign it to multiple categories, then the search results for the keyword search show multiple listings of the same item as the results. Also, it makes the database unnecessarily duplicative to have to create multiple entries for the same item just to assign each item to multiple categories. Need to hire someone to study it, take into account the way it's working now, foresee all possible problems with tweaking and fixing and upgrading it so that nothing is lost in translation and no features are destroyed, and then repaired/upgraded to allow for assigning each item to multiple categories. I'm hoping that it can simply be upgraded without having to be rebuilt from scratch. It would also be helpful to have a review of its functionality and advise on how well made it is. Thank you!