# He was seen for many days by those who had come up with him ... Jerusalem

"The disciples who traveled with Jesus ... Jeruaslem saw him for many days" 

# 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"