how can i make a dialog system?

I personally use this.

First, Insert a RemotEvent named 'DIalogue' in the ReplicatedStorage.

Second, make a part and insert a ProximityPrompt. After, insert a regular Script into the Proximity Prompt, then write this.

Server

local RS = game:GetService("ReplicatedStorage")
local DialogueEvent = RS:WaitForChild("Dialogue")

local Prox = script.Parent

Prox.Triggered:Connect(function(plr)
	DialogueEvent:FireClient(plr, "Hey there! This is a dialogue system! As you can see, the breakers work! It's used as a pause in a sentence.") -- You can use this if you want, useful if you're making multiple dialogues.
end)

This will be used to send a signal to the Client that triggered the Proximity Prompt to execute the dialogue.

After doing these, make a GUI! Make your own design, put a localscript in the TextLabel (Dialogue Text). Then write this.

Client

local RS = game:GetService("ReplicatedStorage")
local Dialogue = RS:WaitForChild("Dialogue")

local Waits = {
	"!",
	".",
	"?",
	";",
	":",
	","
}

local TextLabel = script.Parent

function setText(Text)
	
	for i = 1, #Text do
		TextLabel.Text = string.sub(Text, 1, i)
		
		for Index, Breakers in pairs(Waits) do
			if string.sub(TextLabel.Text, i, i) == Breakers then
				task.wait(0.2)
			end
		end
		task.wait(0.0050) -- Customize this if you want
	end
	
end

Dialogue.OnClientEvent:Connect(function(msg)
	TextLabel.Parent.Parent.Enabled = true
	setText(msg)
end)

And that's a wrap! Test it out!