请翻译：乙方提交设计文件前五天，甲方支付设计费。

The second party submits the design document previous five days, the first party pays supposes the cost

The Part A should pay the Design Fee at least five days before the Part B submits his design documents.
加上at least 是合同常用语，因为5天前含有至少5天，提前到6天当然更好。

建议将甲方/乙方翻成 buyer/ seller

同意~

The Design-fee shall be disbursed by the buyer five days before the presentation of the Design Documents by the seller~