Q: Why do I have to provide my birth date?
Your birth date is a part of your credit card information, we need it to be sure you are the actual cardholder.
Q: How is it possible that on the checkout page my total amount was 165.80 and the invoice you sent shows 252.75?
It is important to remember, that no matter what currency you choose, the total amount in the invoice will be in USD. Further conversion to your currency will be performed by your bank.