Yeah everyone has this problem since Patch 1.30 (6 years ago) I believe.
WESTRING issues in the World Editor shouldn't stop you from doing anything. That issues might be related to the ones that Blizzard didn't fix on the later versions of WC3, specifically 1.30 and 1.31, along with all the other WE and even the game-related crashes and stuff introduced with those versions. Patches 1.30 and 1.31 were made with all the Reforged storage format and features to help get people excited for Reforged and used to the new features. Since it is stored in the modern CASC storage system that is meant to be always checked against the online version, the only languages that work would probably be the ones loaded from the Blizzard server by whoever played that install before you when it was live, who then gave it to you or something.
Speaking of the WESTRING problems you mentioned here, there seems to be a missing language files (for your case, the Spanish) inside the CASC file. For the legacy builds, they are stored in the "War3xLocal.mpq" file, iirc. Therefore, I'm assuming that your game seems to be corrupted.
Also, it seems that you have 2 versions of Warcraft III currently existing in your system, right? tulee suggested that you shouldn't use multiple versions of WC3 in your system, as it might led to an unwanted issues with your game, specifically the registries.