How would I use :wait() to wait until a ScreenGui's position is whatever?

It's a simple do while function that takes rotate into account:

rotate = false --Debounce
function waitUntil(ed,gui) --Create a function for waiting until a GUI is in the right spot
	if rotate == false then --If rotating is false
		repeat wait() gui.Rotation = 0 rotate = false until gui.Position == ed --force it to not rotate until the movement is finished
		return true --return true
	else 
		repeat wait() until rotate == false --if rotate is true wait until rotate is false
		waitUntil(end,gui) --call the function
		return --return nil
	end
end

function rotate(gui) --Create a function for rotating
	rotate = true --set rotate to true
	for i=1,90 do -- or how many degrees you want to rotate it
		if rotate == false then break end --if the tween started stop
		gui.Rotation = gui.Rotation+1 --rotate
		game:GetService("RunService").RenderStepped:wait() --wait one frame
	end
	rotate = false --set rotate to false
end