Hi there, welcome to the forum! I'm going to move this into the 'modding' forum because thats where it fits best.
Much of the in game text is accessible in csv files: strings, rules, hints, hulls, and probably many more, I'd recommend searching for those files and seeing what they contain, but they are quite spread out. Your new versions of them can be packaged into a mod that replaces those so it can be toggled on and off.
There are also probably some hard coded text embedded in scripts, which is a lot harder: afaik quite a lot of the UI is not usually accessible to modders. There have been translations done in chinese for a while so you could try asking in that community if they have good ideas about how to go about it. If you run into specific things buried in scripts you could also either post requests in the suggestion forum or send Alex a PM and see what he says.