[ottix]

I tried to change the language field under Settings -> Film -> Files and Sources, but unfortunately nothing changed.

The source languge setting is only for new movies/tv shows. After changed the source language you also have to select all movies and tv shows in your list and set the language via context menu to that language you want.  

Thank you Dan.
I will immediately try as you say. 

I tried deleting one film, deleting also all the files in the folder, renaming the avi file.
Then I clicked on Update Library.
The system found the new file. I clicked on it and pressed CTRL+I
The file was correctly scraped but still in English   
Plot in English and Title in English.