The "mouth" stands for the person who is speaking. AT: "The things I teach" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
# twisted
"false"
# straight
"honest and clear"
# my words are upright for those who find knowledge
This probably means that those who find knowledge will easily understand that the speaker's words are upright. Here "words" represent a message or teaching. AT: "those who know what is right and what is wrong consider what I teach to be right" (See: [[rc://en/ta/man/translate/figs-metonymy]])