I am 600 days on Duolingo
I tried Spanish, I did not enjoy it. The videos speak Spanish too fast and the words are alien to me.
Every video is transcribed to get much better transcripts than the closed captions. I filter on high quality transcripts, and afterwards a LLM selects only plausible segments for the exercises. This seems to work well for quality control and seems to be reliable enough for these short exercises.
Would love your thoughts!