On earlier conferences, we talked about the concepts of our approach for efficient management of DDI files for documentation applications called DDI-FlatDB. We also showed how to use this approach for bringing metadata into search and dissemination applications, e.g. the GESIS Questionnaire Editor. Now we want to share the experiences using DDI-FlatDB when it comes to convert instances between major DDI versions, e.g. DDI CodeBook 2.5 to DDI Lifecycle 3.2 This conversion of DDI is an absolute necessity to support infrastructures to convert their metadata for the use in new arising documentation tools or for the development of such tools and services. A general point is, that we promised, that we could convert any DDI version to another, just by configuration files. But due to significant different models, e.g. CodeBook vs Lifecycle, we realized, that still programmatic work is needed. Making e.g. question texts, codes and categories from NESSTAR or DDI 2.x variables usable within applications that were implemented along DDI 3.x is challenging. Based on the splitting and entity parsing mechanisms of DDI-FlatDB, we managed to create a converting path from e.g. NESSTAR outputs from various sources into DDI LC 3.2 on variable and question level. This is the first step for indexing questions for the CESSDA European Question Bank search portal or the GESIS ExploreData Variable search portal. We will present the open source conversion tool and describe the process and the lessons learned. Recorded version of the whole session: https://youtu.be/mAXlABqemik