Do u know dis?

A manga where the FL is a demon who is kind of OP, she is possessing the body of some noble lady or something of the sort who made a deal with her. She trains the 2nd knights order so they can beat the 1st knights in some kind of competition, she speaks Elvish to the Elf prince or something which shocks him and impresses him and stuff and helps with a negotiation between their kingdoms. It was something like that, any idea? She is basically OP in every way, magic, swordsmanship, languages, etc and she is blunt but smart and stuff.