We believe this is a great step forward.

我们认为这是向前迈出的一大步。

forward为副词，副词作定语必须要后置，即放在被修饰名词step的后面, great表示程度为前置定语，forward表示方向为后置定语

forward  adv.朝前;向前

We have made a great step forward in our negotiations.  

我们的交涉已有很大的进展.

This view is certainly a great step forward from the'naked ape 这个观点比起 “ 裸猿 ” 自然是进了一大步.

They made a great step forward in their negotiations.  

他们的交涉大有进展.