Translation:This restaurant does not offer beef.
If the objection is to "nie offeruje" being tranlated as "doesn't serve", this is actually a better translation. Restaurants don't "offer" in English.
I totally agree. The English translation "offer" is not idiomatic. "Serve" is correct.
Added "serve". A better Polish word would be "serwować", then. The course teaches the word "oferować" and not "serwować", so we have to stick to that as the main translation even if it's not perfect, but at least your version will work now.