Murder on The Orient Express

I went to see Murder on The Orient Express last Friday.
I was looking forward to seeing it because there was such a gorgeous casting.
But they didn't live up to the hype, I was disappointed.
They were not effective despite being famous actors.
I think Kenneth Branagh as Hercule Poirot was good.
He added had a French accent when he spoke (I know the French accent because my boss is a French man Frenchmen!).
And Johnny Depp was also good.
He was totally a bad person!

Homework. A letter of complain(t)

To whom it may concern,
I am writing to express my strong dissatisfaction with the service I receive(d) during my flight in (with) your airline.
I recently return(ed) from my family holidays in New Zeland on flight SP45628 which arrived at Madrid airp(ort) on 10/25/17.
First of all, I paid (an extra) 50€ for each (person) (4 people) and for (priority boarding) to (avoid the queue) and select our seats. Nonetheless, my family boarded the last for unknow(n) circumstances, and the seats we booked were occupied by other passengers forcing my family to look for empty seats and (travel) separate(ly).
The straw that broke the camel's back was that because there were (no) available seats, my tot traveled on the top of my chest, making it impossible to sleep or to be comfortable.
To make matters worse, the flight attendant(s) were not only unprofessional but also rude, being un(h)elpful (in solving the situation.)
It seems only fair that you should offer a full refund of the (priority boarding) service and (add) extra compensation for the (inconveniences) I suffered.
It would be advisable to take the necessary steps to ensure that such incidents do not happen again.
I expect to receive a prompt re(p)ly to this letter.
Sincerely,

I'm not 100% sure, but I think it's called "priority boarding".  Or maybe that's an American thing.

Prepositions always make me confused.

Hey there!
Prepositions always make me confused.

I need to clarify to my boss.
for example:
Customer asks for it.
We need to put the serial number( on/at/in ? ) the end of purchase order number.
or
We need to put the serial number( on/at/in ? ) the purchase order number ( on/at/in ? ) the end.

Which sentence is correct or both are fine?

Thank you so much.

Both are now fine.  ^_^

Family 2

I have IELTS exam in the next week. And I want to talk about my family in speaking section.

Q. What do you enjoy with your family?

I am very close to my younger sister. I spend all the (my) time with her. We do everything together like eating, hang(ing) out, and talk(ing) about anything and everything. Also(, ) I am very close to my mother but now she is in another country. But (However, )when all family members meet, we usually rent a big house at the beach, eat at a restaurant(, )or have a party.