en_tn/luk/22/59.md

insisted and said

"said insistently" or "said loudly" (UDB)

Truly this man

"This man" refers to Peter. The speaker probably did not know Peter's name.

he is a Galilean

Matthew Matthew 26:73 says that the people could tell Peter was from Galilee from the way he talked.

I do not know what you are saying

This idiom is used to say very strongly "What you said is not true at all" or "What you said is completely false." (See: rc://en/ta/man/translate/figs-idiom)

while he was speaking

"while Peter was speaking"