Yes you may, though always make sure to use the abbreviation for the language codes provided here ( Column "ISO 639-1" ). If you want to translate it into Bulgarian for example ( my native ) you must create a dedicated translation directory here, that corresponds to the code of your native language ( ex. bg ). You must populate that directory with a properties file for the specified script containing language translations related to the value of the console variable gmod_language that stores the language code. The base menu translations can be found in the primary language file when tracking the internal function. Duplicate the English translations file and replace the values with your native:

English  : tool.trackassembly.1=Assembles a prop-segmented track
Bulgarian: tool.trackassembly.1=Сглобява сегментно трасе от предмети

Make sure you use UTF-8 with byte order mask to save your translations characters correctly and always leave the first row empty. Second is actually a game bug and I admit it is pretty weird.

Please also, it is nice to keep the project convention and use two spaces instead of a tab and Linux line endings LF with BOM ( ex. Notepad++ ).

Now, change the language used by the game ( cvar gmod_language ) to your native. Done!

Deyan Dobromirov
Deyan Dobromirov
Deyan Dobromirov
Gedo789
Petar Dimov
General Passing Neptune