Make a New Level

You can remove all previous actors, change the background image and add the actors for the new level or you can create a new (different) world object and set it as the active world.

No one can tell how you tried it. You need to show what code did not work. You also need to be more detailed in your explanations -- how are you making another world? If you remove all actors or set a new different world active, then the old actors cannot still be in the world unless you keep references to them and add them in specifically.