Although I work as hard as I can, I have plateaued at 55%. Sometimes I got to 56% or even 57%. Where am I going wrong?
The fluency levels are not very accurate and does not really matter much, don't worry about it. ; )
The fluency refers to vocabulary not the way you speak. Duolingo doesn't have some words on the course and it is up to you to discover them in reading or conversations.