This can be stated in active form. AT: "The disciples who traveled with Jesus from Galilee to Jerusalem saw him for many days" (See: [[rc://en/ta/man/translate/figs-activepassive]])
# many days
We know from other writings that this period was 40 days. Translate "many days" with a term that would be appropriate for that length of time.
# are now his witnesses to the people
"are now testifying to the people about Jesus" or "are now telling the people about Jesus"