Sounds like your Lang is broken. I will be happy to take it off of your hands for disposal
Now, are you warming your wood before adding it? I know many people will set the wood on top of the fire box to let it get warm before adding it as this can help it burn quicker and cleaner. Are you getting smoke all of the time or just when you add wood? Do you ever get thin blue smoke?
Notice the difference from the one on the left to the one on the right.