Are you talking about this one ?
https://www.esoui.com/downloads/info...lyAlchemy.html
It only contains some strings for the addon afaik see. So it shouldn't alter your login screen or other Strings.
Or are you talkin about another addon?
What if you logout, deinstall the addon completely, just keeping your SavedVariables. Is the login screen etc. still messed up?
Your script should change the texts back to English, if you write it correctly into the chat edit box and press the return key. The game should automatically do a reloadui then for you and afterwards the texts are English again. There is missing a space after /script
Code:
/script SetCVar('language.2','en')