For me, it's helpful to learn Polish phonics: "dzie" = j + yeh, "w" = v, "cz" = ch, "y" = ih (as in sick), "i" = ee, and "n" and "k" are the same as in English.
The PC online version of Duolingo includes 'Tips & notes' pronunciations, near the beginning (phrase lessons section). There are quite a few new accented characters and diphthongs to wade through. Keep them at hand. After that, you can start breaking down the long words, in this case 3 syllables. Take your time. Rome wasn't built in a day... Neither was Warsaw.
Dziewczyny are from teen to young woman. Dziewczynki are little girls through young teenagers
Dziewczynki are nice girls... Dziewczyny are just girls. Teen woman... nastolatki... kobietki.