Keep in mind that GetSimple CMS has in it's basic state two language settings you can or have to edit. The first one is for the whole admin interface and it is located in admin/lang/ folder. You can add whatever language file you want here, once it is correctly coded.
But the trick comes with the row number 484 (GetSimple Version 3.2) in language file. The property “CKEDITOR_LANG” sets also the second language file the system needs. As you can guess, it is for CKEditor area language settings. Therefore you have to be careful if this setting matches the second language file, editor's one. It is located in /admin/template/js/ckeditor/lang/ folder.
If the setting for CKEditor area language is pointing to the missing file, you won't see the WYSIWYG area and you won't be able to add or edit the page body texts (unless you'll uncheck WYSIWYG possibility in administration settings page).