Try this out to hear native speakers. But I don't hear any problems with this sentences. Remember you are at the very beginning you'll get used to it. https://forvo.com/search/%CE%B4%CE%B9%CE%B1%CE%B2%CE%AC%CE%B6%CF%89/
What was the mistake? When your sentence was rejected there was the correct sentence at the bottom of the page. You should have compared it with what you wrote to learn what your mistake was.
Read the other comments on this page to get some ideas about how to learn on Duolingo.
Did you make a Report? YOu will also find out how to do that on this page. And also look here: