Since the last update of warcraft 3 reforged the editor was changed to English language someone knows how to change it to Spanish
See if you can get UI\WorldEditStrings.txt and UI\WorldEditGameStrings.txt exported from the old game version in whatever version you had with Spanish language, then import it in your map and see if it overrides the editor data. I think it would be worth a shot. It might or might not work.
But also, make sure you select Spanish while installing. Maybe do a reinstall and get that popup and choose spanish.