OP Magician

#1
I don't remember much about this novel but a few things.

He uses a necklace for translation. The Princess likes him. He makes really good weapons because of the refining process he does and they are considered "the best". He is younger than what his body is. One of the parts he befriends a dragon that is disguised as a human and becomes part of his family for nobility and such.

The easiest part to remember it from is "He uses a necklace for translation" Because in one of the parts a thief that takes fancy to him steals his necklace.