How do I make an if that triggers if something is there?

if game.Workspace:FindFirstChild("Brick") then
--do stuff--
end

if then and ends work like this

if true then

end

it has to be true to actually do it so it's an if statement if its false then it wont carry out

:findfirstchild("") if its found returns a true

Hey! I'm BlackOrange here to help!

First to check if something simply is there, we could use something as simple as a if statement to check either something is there or not then decide if we should execute the code.

-- ServerScript

if game.Workspace.Part then

end

-- OR

if game.Workspace:FindFirstChild('Part') then

end

Now if you mean detect by .Touched or walking through a door and trigger something then using .Touched may be the best option:

game.Workspace.Part.Touched:Connect(function()
    -- trigger something
end)

Now .Touched will fire many times so we should add a debounce

local d = true

game.Workspace.Part.Touched:Connect(function()
    if d then
    d = true
    -- trigger something
    wait(1)
    d = false
end)

Anyway this is probably how you "Detect" something. There are other ways such as :IsA() and many more ways to identify what is what.

Best of luck!