GW2 Chomper delivery mission Shoot n' Scoot ... xbox

i need help i ibeen trying to  do this for  my 7 years old son   only  games  i play myself is call of duty   and racing   am not sure why i cant  do something so flciking easy  i keep dieing or something -   i    spent 3  full days  trying to do this  for him  as he cant  do  it  himself  ----- i dont understand  why i cant do        if anybody  got the  time to    try help me out  or  do it  for me  thanks alot   gametag  is  pro55gaming  ty