I think it is great Duolingo teaches so many idioms, but how do I remember them all? I use the strengthen test, but it leaves out a lot of the idioms. Can someone please tell me something I could do to remember all of the idioms?
You could redo each lesson over and over again until you have all of them down. You don't always have to press the "strengthen" button. Just redo the lessons and it should help. Also, you could simply research idioms and see what they give you. :)
It will be very helpful to start taking notes and repeating them to yourself. However, the best way to remember is using them in a conversation. Even if you say something wrong it's going to help on the next time you speak because the second time is always easier than the first one.