Help me! Instance.new("BillboardGui") is not creating Billboard gui.. Why?

Try This!

local billboardgui = Instance.new("BillboardGui")
billboardgui.Parent = game.Workspace

Or

Instance.new("BillboardGui", game.Workspace) --put the objects parent after the comma.

What you're doing here is pretending defining game.Workspace as a variable and trying to replace it as a BillboardGui, so it's not gonna work on a lot of levels :)

Instead, make BillboardGui's Parent the Workspace. Or in other words, put the BillboardGui inside the Workspace. You can do this easily because Instance has another property where you put the Parent. Like this:

Instance.new("BillboardGui",game.Workspace)

That isn't how you create things.

You should either set the Parent property of BillboardGui after creating it to workspace, or put workspace as the second argument of Instance.new (which is not recommended)

So, 1st way:

local bg = Instance.new("BillboardGui")
bg.Parent = workspace

2nd, (not recommended by most people because it decreases the performance by like 0.004 seconds or more depending on what you do) way:

local bg = Instance.new("BillboardGui", workspace)