What does 我知道 and 应该的 mean in this dialogue?
In this context:

我知道 means 我現在知道了 (now I know)
应该的 means 人與人之間互相幫忙是应该的 (people helping people is obligatory)

The one asked for information said &quot;我(現在)知道(了)&quot; to confirm he has received the information. If he just said &quot;好，谢谢&quot; (good, thank you), the one who gave him the information could not be sure that the information he gave was successfully passed along.
After someone thanking you, saying 不客气(you're welcome) is a polite respond. And that should be enough.
Adding &quot;应该的&quot; (it is a right thing to do) is to show humbleness.
Implying: My action is not a grace I grant you, but an moral obligation between common folks, no need to be too grateful