How do I make a 'story-mode talking text'?

you could have a typewriter function which types the text,using string.sub(), so lets say you want the script to activate 10 seconds into the game, we need a function to type the text and make it wait 10 seconds. place this script into the text UI

local function TypeText(Txt, TimeToType, UI) -- We Use "TimeToType" to see how fast the typewriter will be (e.g will it take 5 seconds, 10 seconds etc) and "UI" to show which UI it will type on
    local TextLength = string.len(Txt) -- Find How Long The Text Is
    local TimeToWait = TextLength / TimeToType -- Divide 'TextLength' By how long it takes to get how long each character of the sentence will take to be typed.
    if not UI:IsA("TextLabel") or not UI:IsA("TextBox") or not UI:IsA("TextButton") then
        error("Script Error: UI is Not A TextLabel, TextButton, Or TextBox")
    elseif UI:IsA("TextLabel") or UI:IsA("TextBox") or UI:IsA("TextButton") then
        for textCount = 1, TextLength, 1 do
            UI.Text = string.sub(Txt, 1, i)
            wait(TimeToWait)
        end
        UI.Text = " "
    end
end

wait(10)
TypeTxt("Welcome To PlaceName!", 3, script.Parent)

---[ OR SOMETHING LIKE A SHOP ] ---

local Distance = (workspace.ShopPart.Position - game.Players.LocalPlayer.Character.HumanoidRootPart.Position).magnitude

repeat
    wait()
until Distance < 30
TypeTxt("Welcome To The Shop!", 2.5, game.StarterGui.ShopTextThingy)

maybe ontouch

put this script into the part you want the players to touch

script.Parent.Touched:Connect(function() -- function
--make text appear here
script.Disabled = true -- this makes sure the script won't activate again
end) -- end