Student or Learner
1) Use barricade to form the area that the customer will line up.
2) By doing that, it will disrupt the flow of the line/queue.
3) They don't line up.
4) Is their culture not to line.
1 Use barriers to set out the area the customers will queue in.
2 Doing that [I'd use 'this' if you're referring to sentence 1] will break up the flow of the queue [If you mean those channels they have to force people to go through a series of turnings to stop pushing, then this sounds negative- how about 'reduce the pressure' or 'prevent pushing' etc]
4 In their culture they don't queue/form queues.