Hallo expest
First a warm wellcome at our internet-forum.
If you are able to translate German into Russian than it is possible but it is a lot of work.
You have to open the file "__edain_data.big and extract the lotr.str. There you will find all the descriptions in German. Overwrite it with the Russian descriptions and save the new descriptions. After that you have to overwrite the old lotr.str file in the __edain_data.big with your new one. If you don't do a mistakes it should work.