If there are only German voice files in the Voice folder then it cannot use Polish. There are several types of garmin voice files, all with extension .vpm but different files are for specific devices also some are TTS and others non-TTS. Generally, most Kenwoods use the files from nuvi 34/35x0 devices but not all. Be careful because the wrong TTS file could brick it. Upload the German voice files from your Voice folder so we can compare them.