You don't need to delete it, it's no big deal - duplicates of all sorts happen all the time and if they end up somewhere they shouldn't be, users and/or moderators sort it out.
You could also repost somewhat earlier if there's major rework/features, etc - the point of this stuff is not to discourage people from showing their own work, just to avoid excessive samey-ness.
The issue is that nobody speaks "classic" arabic in day to day life, so its not very useful. The egyptian dialect on the other hand is the most widely spoken dialect and understandable by most arabic speakers.
