Dare, Itsu, Doshite, Nani, Doko, doo~ 5W2H are some of most commonly used questions in Japanese.
“What” can be both “nani” and “nan” depending on what comes after it, “what” is nan when it comes before words starting with “d” and “to”
When Dare, Itsu, Doshite, Nani, and Doko are used as subject, “ga” is always used as the particle because these words are highlighted and emphasised. Never use “wa” as particle behind the interrogative words.