How to pull words out of known words

i acidently put all the words form a lesson in the known words count and it wont let me get them back where i can actualy learn them what do i do.
i ended up deleating my account and remaking it but i dont want to have to do that every time some thing like that happens what do i do.

Just re-highlight all the words you don’t know.Then they appear blue again.

thanks lol