2 sentences

1. 我们要先调查研究，而后再下结论。

   wǒ​men yào xiān diào​chá yán​jiū, ér​hòu zài xià​jié​lùn.

   We should investigate and study first, and then draw a conclusion.

   Source: Dong Chinese Dictionary

2. 既然事关重大，你应该三思而后行。

   jì​rán shì​guān​zhòng​dà, nǐ yīng​gāi sān sī ér​hòu xíng.

   Since it is a matter of great importance, you should think twice before acting.

   Source: Dong Chinese Dictionary