If the German sentence means that Duolingo is my employer (and not, as someone suggested, "I am working at the Duolingo course") would "I work for Duolingo" be accepted?
Thanks! It certainly sounds a lot more natural. In English, we would say, "I work at a language centre", but when, as here, the employer is named, we more usually say "work for". Thanks again.
I don't know why people marked you down for this.
"I work with Duolingo" suggests that Duolingo is a person that you work with. In this case Duolingo is a place to work, so I would write "I work at Duolingo" instead.
I realize that this is a year late, so you might have figured this out on your own :)