Fan translations are run entirely by the players :) I'm a solo dev so I don't have time to oversee translation work personally (although I'm always happy to answer questions translators may have!) but if you feel like undertaking the project yourself on Discord, that would be amazing!
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Different translators have different methodologies, but for the most part I think they tend to use the "UnRen" software to de-encrypt the game files, then load everything up in Ren'py and translate page by page.
I've never done it myself, so I can't be much help on the subject, but there's already a Spanish translation posted so you could ask the translator about their method in the post's comments :)