Questions & Answers about Wij zijn nog niet in het stadion.
Why does nog niet translate to "not yet"?
Literally, nog niet translates to "still not." In Dutch, this combination is the standard and only way to express the English concept of "not yet."
Why do we use niet instead of geen to negate this sentence?
You use niet here because you are negating the prepositional phrase in het stadion (the fact of being in the location). You only use geen to negate a noun that has no article or uses the indefinite article een (a/an).
Could I change the word order to Wij zijn in het stadion nog niet?
No, that would sound unnatural. Dutch strongly prefers to place adverbs of time (like nog niet) before expressions of place (like in het stadion). A good rule of thumb to remember for Dutch sentence structure is: Time comes before Place.
Notice that it is stadion instead of "stadium". How does this word behave in Dutch?
Unlike the English word that ends in "-um", the Dutch word keeps the -on ending. It is a neuter noun, which is why it uses het, and to make it plural you simply add an -s (stadions).