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!