When someone greets you with "buenas noches" (good evening) in Spanish, a suitable response is simply repeating "buenas noches." You can also add a friendly phrase like "Igualmente" (likewise) or "¿Cómo estás?" (How are you?).
So, the exchange could look like this:
- Person A: "Buenas noches."
- Person B: "Buenas noches, ¿cómo estás?"
Feel free to adjust the response based on the context of the conversation!