Multi language is much work.
Since V1.30 (casc) there is a new approach.
You create copies of the files that contain text/sounds/images for the player translate them and import them into your map in a folder meant for that language.
(V1.31.1 List, reforged might have more)
_Locales/dede.w3mod
_Locales/enus.w3mod
_Locales/eses.w3mod
_Locales/frfr.w3mod
_Locales/itit.w3mod
_Locales/kokr.w3mod
_Locales/plpl.w3mod
_Locales/ruru.w3mod
_Locales/zhcn.w3mod
_Locales/zhtw.w3mod
your map only needs to contain the ones you support.
In normal setup your map stores texts of object Editor and fixed gui strings inside a file called war3map.wts, which world editor can import and export under menu File ex/import strings.
The one in the root of your map is used when no localized one is found for the user.
war3map.wts
_Locales/dede.w3mod/war3map.wts
_Locales/enus.w3mod/war3map.wts
_Locales/eses.w3mod/war3map.wts
_Locales/frfr.w3mod/war3map.wts
_Locales/frfr.w3mod/war3map.wts would be the one with france texts and is used when the game runs in frFR locale.
this also works for other files.
You can test a language by forcing Warcraft to start with a wanted locale and playing your map creating a shortcut of the warcraft 3 exe (not the launcher).
Example for my warcraft 3 shortcut.
"F:\Spiele\Warcraft III\V1.31\x86_64\Warcraft III.exe" -locale enUS -nowfpause -loadfile
In reforged you should add -launch before -loadfile
Now you drag drop your map into the shortcut, although the map you drag & drops has to follow the max path lenght warcraft 3 map. So for testing I suggest to copy it into desktop and run it from there.
Warning:
Multi language is much work.
Warcraft 3 V1.31.1 World Editor did some junk with the imported localized files when I pressed save map it overwrote the default none locale files with the ones from the current imported local, hopefully it is fixed in the version you edit.
Or it might be smarter to add this locales using a mpq editor and only in the version you want to release.
good luck