@Pieter Boelen , I have spoken with @Homo eructus by a private conversation, and I decided to help him with his work of translating the game into spanish language, as I am too from spain I'm not the greatest modder, but I will be sure to contribute or help him as much as I can.
Welcome aboard! As promised, here's a sample of what I've done so far.
Common.ini and interface_strings.txt could be useful because a lot of main game concepts are in there (ship types, officer jobs, cargo types...), so if they appear again further along, you can match them with what I've already done and avoid having the same thing named differently. The others are randomly picked to give a general idea of the file types. They sure have some typos, spcially as I typed some of them with a busted keyboard (I still find a few every time I check), so feel free to correct any mistake you find and send the files back to me.
PD. Of course in the final version, the folder will be named SPANISH.