I’m currently nearing a 2000-day streak and have repeatedly gold-starred the German course as they add more content, and Duolingo isn’t the only app I’m using.
Despite this, while my vocabulary is OK, I don’t conjugate even close to correctly, my grammar in general sucks, and I can only comprehend real-life spoken German if the speaker talks very slowly and clearly and uses a sufficiently short sentences — from experience, the sort of conversation you’d find in an interview in a general interest magazine in the waiting room of a Hausarzt.
I’m also trying to learn Arabic on Duolingo. Over a year into that course, I still can’t even read the entire Arabic alphabet.