Methods To Quit Smoking

I quit smoking about 3-4 weeks ago, and I keep coughing up brown/black stuff. Will this eventually stop? Will my lungs clean themselves back to a better condition after a while?

I have quit smoking for good. But, I have smoked on and off for about 2 years. I’d say my longest period of smoking was about 9 months. About a thimble size amount of pot being smoked once a day. Of course also the rare time of more than that. No cigarettes, just marijuana .