I am a native italian and my (british) gf has been learning italian using duolingo, I found that very often the pronunciation of words is incorrect and phrases built together in the listening exercises sound pretty robotic and do not resemble the italian intonation, making them sometimes quite hard to understand even for a native speaker. Rather than composing sentences couldn't you find somebody that spends a few hours recording all the sentences you use? If my gf spoke italian with the same accent as the voice in duolingo she would sound like a joke. Besides this issue, keep up the great work!