According to game license you are allowed to do so in a form of mod triggered by content package. Also please improve your Polish in this post.
See my Polish translation mod here:
https://undertowgames.com/forum/viewtop ... =20&t=9802
You are not the only one.
I can give you my permission to use this texts.xml file under one condition: You will mention yourself as creator of content package itself but me as the only creator of this texts.xml file. I allow you to edit it.