If you use by Link2012:

before installing any mods. If your text disappears or turns into "GXT_ERROR," simply pasting the original file back into the folder will fix it instantly. Are you trying to fix a specific error in your game text, or are you looking to the original file for a fresh install?

If you absolutely must manually hex edit:

To modify or restore the original american.gxt Grand Theft Auto: San Andreas (GTA SA)

: Many mods replace this file to add custom mission text, but if a mod is uninstalled poorly, it can leave the game text broken or missing. Language Fixing