Problem: The client needs to change the language of over 400 posts that were incorrectly duplicated and translated within the same language instead of being assigned to their respective German and Spanish versions.
Solution: We recommend the following steps: 1. Make a database backup. 2. Export the posts to CSV files for each language using WP All Export and WPML documentation. 3. Delete all the posts from all languages and remove them from the trash. 4. Import them again, ensuring to select the proper language during the import process as outlined in the WPML All Import documentation.
If this solution does not seem relevant to your situation, please open a new support ticket in the WPML support forum.