英语翻译最好口语化一点；1,我在组装机器,关键是连杆位置要放恰到好处.2,这一步是关键.3,他正在测试这台机器的压力平衡

I am asembling the device ,the main point is that the conbination is at the right place.
this step is critical
he is testing the pressure balance of the device .
the testing of the device don't pass