The short answer
Uploaded model and CAD files are kept in Dlubal-managed object storage in the EU. The current default region is Falkenstein, Germany. Chat messages, attachments, drawings, and project data are stored in the CALC application database in Germany. When you connect RFEM or RSECTION locally, the complete desktop model stays on your computer. Only information you explicitly request is returned to the chat. Storage is in Germany with Hetzner Online GmbH (Industriestr. 25, 91710 Gunzenhausen): the application database in its Nuremberg data center and uploaded files in Falkenstein. Backups also stay in Germany.