“我们一直有着很好的合作”请翻译成英文，谢谢！

We have been in good partnership all along.

表示合作，我一直都喜欢用 partnership 一词，因为这个词可以理解为“合作伙伴的关系”，而不仅仅是“合作”。用 have been 表示动作的延续性。如果这里不是 be，那么用完成进行时是非常适合的，如 have been cooperating，那么这个句子也可以说:
We have been cooperating all the time.

We have been cooperating well for a long time.

We've been in good cooperation~

We have had very good cooperation