Hello and welcome!
ArcExplorer is already a good start.
You'll want to find the text_en file and extract all the single text files in there. Then you can just translate the different entries for each "tag".
(Those are what the game uses to insert the text - do not change.)
If the gender and amount of an item matter for adjectives in Greek, also have a look at other languages than English.
There you will find item names with {ms} on such behind them, which designates those, e.g. ms=male singular.
Which in turn is used when adjectives can take different forms. Then you will see these versions written in a string like {ms}grand|{fs}grande.
To test them out, you could just make a new mod and paste the tags you have into its modstrings.txt
Then once you are done with all you'd ideally have to use the Archivetool to pack them back into an .arc - maybe one that people can just replace another language with.
But I'd worry about that when you get there.
