If the RNS 300 is from a Japanese import, it may not have European languages available, requiring advanced re-flashing or replacement, though the methods above are the first steps to try.
Your RNS 300 might be in a special service mode or locked. Try this alternative path: how+on+rns+300+change+language+new
The Renault RNS 300 (also known as or similar basic navigation/audio unit) typically features a monochrome or low-resolution color display. Unlike modern systems, the language setting is not always found in a dedicated "Language" menu. The method depends on the firmware version. The Tourist Mode: A Story of the Misunderstood
This indicates a failed internal memory battery (a supercapacitor on the circuit board). The unit cannot store settings. You will need to change the language every time you start the car. Unfortunately, this requires a professional electronics repair or unit replacement. Unlike modern systems, the language setting is not
is a legacy "entry-level" monochrome navigation unit found in mid-2000s Volkswagen, SEAT, and Skoda vehicles.