"found many gentile people gathered together". It is implied that the people Cornelius invited were Gentiles. (see: [[rc://en/ta/man/translate/figs-explicit]])
## it is not lawful for a Jewish man ##
"it is forbidden for a Jewish man"
## You yourselves know ##
Peter is addressing Cornelius and his invited guests.
## So I ask you why you sent for me." ##
Though Peter is directing the question toward Cornelius, "you" includes the Gentiles present (plural).