# For this purpose
"For this reason"
# I was appointed a herald and an apostle
"Christ made me an official messenger and an apostle"
# I am telling the truth, I am not lying
With these two comments Paul emphasizes that he is telling the truth when he says that he was appointed to be a herald, an apostle, and a teacher. Some translators may prefer to put these comments at the end of the verse.
# in faith and truth
"about the message of faith and truth" or "about the true faith"