To answer your question about the English punctuation, it's better to use the colon there. Colons act as a break in the sentence the same commas do, but are used to define new information. For example: <-- (That's an example in itself, haha... okay, but really an example now: )
My question: Where were you on the night of the fifth?
A comma is best used to keep the flow of the sentence and to create a pause where needed or to make mention of information that a sentence can be completely understood without. For example:
The sun, brightly shinning its blinding light, seemed to engulf the world before me.
As you can see, the information in between the commas can be completely left out and the sentence's meaning would remain unchanged. Commas are also used to list things out, but that's the most obvious use, which I think you know of already.
e.g. "Buy eggs, milk, and bacon from the store."