You remember from the SCD1 trainings that if you delete a language in Sitecore, you will also delete the content at the deleted language. Though, it is possible to maintain the content at the deleted language - and if you afterwards add the deleted language, Sitecore will replace the content into the language. How to do so - simply change the value attribute from true to false... more to come...
< !-- AUTO REMOVE ITEM DATA Indicates if item data is automatically removed from a database when a language is deleted. Default value: true -->
<setting name="Languages.AutoRemoveItemData" value="false" />