#2 - Feb. 24, 2013, 1:11 p.m.
First, your English is great!
Secondly, yes, that is a known issue and we’re sorry! Here’s the official messaging on this issue (and the goods news that you WILL get the sale price):
The Order Summary is slow to update when changes are made. The promo price will appear on the “Order Summary” once you enter all of your credit card or PayPal information in the fields provided.
Promo Sale offer applies only to Digital Edition and Digital Deluxe Edition purchased through buy.guildwars2.com from 7pm CET (10am PST), 22nd February 2013 to 9pm CET (12pm PST), 25th February 2013.
If your friend continues to have difficulty, please ask him to contact Support by filing a ticket through the “Ask a Question” tab on that linked page. They will be able to assist him.