The Language Conversion command converts description or switch position component text from one language to another. When AutoCAD Electrical finishes, it displays a report listing what was successfully translated and what was not. You can use this report to surf to the problem areas (where a phrase could not be translated) and make manual edits one by one.
You can add more phrases to the translation table using the Edit Language Database File tool (Project tab 
Other Tools panel Edit Language Database) and rerun the language swap to obtain more satisfactory results.