"우리는 이제 이해했습니다."
Translation:We now understand.
Why is the translation in the present, while the verb itself is in the past?
This may be a bit difficult to explain (although I have done it for other verbs that are used similarly)…
It is in the past tense because the fact that you are understanding it now is due to you having a moment of insight at some point in the past. Think of the past tense as referring to having experienced that moment of insight. By having that moment, you are now continuously understanding in your present state. The Koreans to not refer to this state, but to that moment in the past.
이제 is lot more often used when something changed. Like "now I understand!"