哪位能帮忙翻译一下，多谢！
以下是合同中关于分期付款内容：
15% of the contract price will be paid airmail within 34 days after the buyer receiving a performance bank guarantee with the same equivalent amount issued by the seller, this bank guarantee will be valid from the date of its issuance unit the date of the buyer received the goods。
75% of the contract price will be paid by airmail within 55days after successful commissioning and three months smooth operation and receiving a bank guarantee for quality warranty for a period of 15 months from foreign trade company delivered or 30 months from shipment,which comes later.
