not all transaltions stores inside xml. Other parts, that we calls "descriptions" stores in it's own tables.. for ex.: product name, category name, menu item title etc.
What you call "top menu"? admin or storefront side?
if storefront - you can change title by design->menu->edit menu item. Just change content language (language switcher in the form heading) and change text. Menu title(name) is a "description".