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