Ι often forget to switch between english and greek script as I type when asked to tpe what I hear - my answer is then marked wrong. The Spanish version of Duo lingo tells me the naswer is not in Spanish and asks me to try again which is less irritating. Could this option be worked into updated Greek versions?
"τέλεια" is an adverb however in English we wouldn't use an adverb in this sentence. Here's a good set of dictionaries:
So, we have grammatically correct Greek and English. See the comments below.