My Roblox Gui does not update while in game

Question

In my Roblox game, I'm trying to do 2 things with my UI: 1. I am trying to make the "Coins: " text = "Coins: " plus the number of coins the player has. 2. I am trying to make a shop Gui show up when you touch a part. But whenever it's updated, it doesn't show up in-game. I checked the properties while running the game and it says "Coins: 10" and "Enabled: True" but it doesn't show up in game, here are some images:

here is the coins script:

local part = script.Parent
local click = part.ClickDetector
local coinsGUI = game.StarterGui.ScreenGui2.TextLabel2
_G.damage = 1
local health = 10
local dealingDamage = false
_G.coins = 0
local coinsWorth = 10

local function onClick()
    while health > 0 do
        dealingDamage = true
        wait(1)
        health -= _G.damage
        print(health)
    end
    dealingDamage = false
    health = 0
    part.Transparency = 1
    part.CanCollide = false
    print("okay that works")
    _G.coins += coinsWorth
    print("that works too")
    coinsGUI.Text = "Coins: " .._G.coins
    print("okay")
    part.Transparency = 0
    print("i dont see what the problem is then")
    health = 10
    part.CanCollide = true
end

click.MouseClick:Connect(onClick)

and here is the shop script:

local part = script.Parent
local confirmGui = game.StarterGui.ScreenGui
local yesButton = confirmGui.TextButton2
local noButton = confirmGui.TextButton

print(confirmGui.Enabled)

--local function onTouch(coolPerson)
local function onTouch(coolPerson)
    print("function ran")
    local parent = coolPerson.Parent
    if game.Players:GetPlayerFromCharacter(parent) then
        confirmGui.Enabled = true
        print("detects player")
    end
end

part.Touched:Connect(onTouch)

Answer 1

You are modifying the value in StarterGui, not the one in the player's GUI. StarterGUI is only used when a new player joins to give them the GUI.

Modify the GUI inside of game.Players.[PlayerName].PlayerGUI.

In your case, you should do the following:

Script 1:

[...]
game.Players:GetPlayerFromCharacter(parent).PlayerGui.Enabled = true
[...]

Script 2:

[...]
local function onClick(plr)
    [...]
    plr.PlayerGui.ScreenGui2.TextLabel2.Text = "Coins: " .._G.coins
    [...]
end
[...]