I sent a letter to Qui Minnan at the following address: Ren Yu Lan, 491 South Chang'an Road, Xi'an 710061,China but my letter was returned to me with the message that my letter could not be delivered, why is that and should I try again?

Would you please show me the correct way to Address a letter to the UK. a visual example would be excellent. The reason i ask this question, i recently posted a letter to the UK. from Hengyang City and the letter came back to me, i was forced to pay postage again which i think is utterly unfair and i want to make sure this does not happen again.
Please this is urgent.
Thank you.

I hope this message finds you well. I am writing to inquire about the delivery status of a letter I sent from Budapest, Hungary, to Duke Kunshan University, UG Residence Hall F, 3F, Duke Ave 8, Suzhou, Jiangsu Province, China. The tracking number for the letter is RR517066906HU.
As per the tracking information, the letter is currently in Beijing. Could you please provide me with an estimated delivery time for my letter?

Thank you for your assistance.