hmmm. duolingo gives a little bit different phrases, like 饺子 instead of 水餃. 服务员 instead of 服务生. 睡觉 aka sleep also writes differently. are you chinese? what dialect is this?
I use the traditional Chinese characters, so the characters for sleep for instance look different than your Duolingo, which uses simplified characters. You can watch my video on the difference between them and why learning traditional first is a bit better. I also use the other words you mention because I learnt Chinese in Taiwan and we use these words. The words you mention are also correct, just different and used in China. Thank you for watching and your questions.