求精英帮忙翻译一些让我纠结的句子

1.前半句可以用 like I have promised you before, before是‘曾经，以前’ 的意思 用在这里比较符合你的句子，后半句 if you purchase 5 pieces(PCS), I can give you a discount price。
2.Please inform me of any progress that needs my cooperation. 你原来的'where need my cooperation'是病句，因为你的句子是在假设事情的发生，所以一旦他们需要你的帮助，这个需要（need）应该是过去式，所以是（needed）
3. I originally planned on sending you a Thanksgiving card like other clients. - 意思是： 我本来打算给你寄一张感恩节的祝福卡片，像其他客户的一样。
你如果想加上‘但是却不是你所在国家的感恩节’， 可以用： However I have realised it isn't Thanksgiving in the country you are in.

1.就像我曾承诺过你的，如果你买了5PCS的话我可以给你优惠价格.
As I once promised to you,I would offer you the favourable price if you bought 5PCS.
2.有任何进展需要我配合的地方请告知我。
Please inform me of any progress when my cooperation is helpful/is needed.
3.我本打算像给其他客户一样给你寄一张祝福卡片的。
I intended to post you a Blessing/Thanksgiving Card as I had done to other customers.
后面可以续接but it was cancelled considering the different date for Thanksgiving Day in different countries.
祝你开心如意！O(∩_∩)O~~

1. Just like what i ever promised, the price will be more favorable based on qty of 5PCS.
2. Pls keep me informed of the progress of manufacturing where requires our cooperation.
3. I planned to send a Thanksgiving card to you like that of other customers.