How does it work
I just wanted some tips for this website because sometimes I run out of hearts and it just says retry but if i do not know that material then how does that work if you can not beat it in so many tries do you like make it easier or give us more hearts or what?
Analyze your mistakes. If you don't understand some of them, don't drill the phrases but look for explanations. Use grammar sites or discussions here. Those that you understand after being showed the correct answer just need practice.
Keep retrying it until you get it. ;) The idea is that one learns even as one makes mistakes. You may need to jot down some notes and study a bit, on Duo, online, or with a book, to fully understand things so you can get through a lesson before you lose all your hearts.