So i have a script for specific server but i want to make it to detect when quest is completed can anyone help ?

Script: 
 

var
  i:integer;
begin
  print(user.target.attackable);
  while true do
  begin
    delay(user.cast.endtime);
    for i:=0 to CharList.count-1 do
    if ((not CharList.Items(i).Dead) and (not CharList.Items(i).Name.Contains('Bot'))
      //and CharList.Items(i).attackable
      //and CharList.Items(i).InZone
      //and (CharList.Items(i).ClanID<>User.ClanID)
      ) then
    begin
      engine.settarget(CharList.Items(i));
      Engine.UseSkill(19);
      break;
    end;
    while ((not user.target.dead) and (not user.dead)) and (not user.target.Name.Contains('Bot')) do 
      begin
      Engine.UseSkill(19);
      Engine.UseSkill(369);
      Engine.UseSkill(101);
         delay(user.cast.endtime);
      end;
    engine.canceltarget;
  end;
end.

Is it even possible with this script ?

Yes, it's possible with Engine.QuestStatus method
Example: https://adrenalinebot.com/en/api/example/check-quest-stage-by-id