There are various ways to implement this. If you want to have complete control over the flow of conversation, it would be easiest to use a multiple-choice extension like “Hybrid Choices” by AW Freyr: extensions/Hybrid Choices.i7x at 9.3 · i7/extensions · GitHub
If you instead use the traditional method of conversation, i.e. ASK NPC ABOUT … or TELL NPC ABOUT …, then it’s more difficult to establish a consistent flow, because the players can in principle ask about anything at any time.
You can take a look at Eric Eve’s conversation extensions like Conversation Nodes, which come with code examples. They are really good, but require a bit of learning and overhead to get going.
I’d also recommend checking out the Recipe Book, section 7.6 (Getting Started with Conversation) and following.
Having said all that, here’s a very bare-bones example without using any extensions:
The Conference Room is a room.
Adam is a man in the Conference Room.
Berenice is a woman in the Conference Room.
Meeting Stage 1 is a scene.
Meeting Stage 1 begins when play begins.
Meeting Stage 1 ends when the time since Meeting Stage 1 began is 4 minutes.
Every turn during Meeting Stage 1:
say "Adam says: [one of]'Our plan starts with the first step.'[or]'We will follow that with the second step.'[or]'Finally, we will implement the third step.'[or]'That's it. Any questions or ideas?'[stopping]".
Check asking Adam about something during Meeting Stage 1:
say "Adam is busy explaining the plan. He will answer questions later." instead.
Check asking Berenice about something during Meeting Stage 1:
say "It would be rude to talk to Berenice while Adam is speaking." instead.
After asking Adam about "the/-- plan":
say "You ask about the details of the plan. Berenice nods and asks: 'Yes, aren't there some prerequisites before the first step?'".
After asking Berenice about "prerequisites":
say "You ask Berenice what kind of prerequisites she means. Berenice says: 'It's what I call step 0.' Adam nods, 'Good point.'".
Test me with "z/ask adam about first step/ask berenice about plan/z/ask adam about plan/ask berenice about prerequisites".
This uses a scene to constrain the player a little bit while the first NPC explains something over several turns, before conversation becomes possible. You could chain several scenes together in order to simulate various stages of the meeting, where different questions are allowed.
As I said, this is just a very basic example, showing one possibility to get you started. In a game, you’d also want to handle “TELL NPC ABOUT …”, not just “ASK NPC about …”. And you might want to enforce that the players can only ask about something after they heard about it, and so on.