I dunno exactly which file belongs to whitch content.
But "Text/dialogs" deals with all ingame dialogs, while "Text/cuts" deal with all videos, narrations, and cutscene, and "Text/game" deal with all the menus, inventories and various logs. You will certainly find what you need in the "game" folder.
Also, there are text that are, in fact images. If you want to change it, you will have to find the corresponding images, and use photoshop to replace the text while trying to keep them beautiful. It is likely that the main menu is amongs those things.