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What does this mean? And why does it go down in stead of up after each lesson completed?
When I was learning French (I finished) whenever I completed a lesson, my "percent" always went up. You may want to report this to a staff. Maybe your tree is decaying and lowering your "percent"
Yes, I that happend to me as well in the beginning, but now it goes down after completing each lesson. When finished a chapter, fx Adverbs, it goes up again, and then down after each lesson, it´s really frustrating... I´ve sent a message to duolingo support, but no response yet after four weeks.
I wouldn't really know, but to hazard a guess, maybe it declines because some of your older words are weakening? I mean to say, its internal model thinks they are weakening, and so it is penalizing you because it has not observed you practicing them inside duoLingo.