> mkVI on e46

Undoubtably youmean a mkIV. BMW never made a Mk6 nav

> is there a way to change the text language of the navi?

The Mk4 can have 3 x languages loaded. These are changed in the Settings screen

IF you don't like the 3 x languages you currently have loaded, you can change them. Possible languages are GB, US, IT, FR, DE, ES, NL, RU.
You can have any 3 loaded.

You can ask your BMW dealer to load new languages, or you can do it yourself with my NavCoder software.