Hi,
I got a bit carried away tonight and did a pass through the whole English localization of the addon, updating many of the translations & grammar issues. It might not be perfect, but I did change a fairly significant amount. For the few that I didn't really understand, I just made up a couple of new names for them.

I thought, since you asked about help with translations, that I should post the file here.

Also, if the addon author doesn't see this, you can update it yourself if you feel like it, just go to the folder Classic Achievements > localization and replace the en.lua file with the one I've linked below.

I wasn't really sure how/if you'd want me to contribute directly here on GitHub, so I've put the file on Google Drive.
Drive Link (I hope I turned sharing on?)

Hope this is helpful!!