Welcome to Mayo Connect, and congratulations on quitting smoking!
First, as a former smoker of any age, it would be a good idea to get a complete physical examination, including a chest x-ray, to determine your overall health. The severe shortness of breath that you describe could be due to many things, and it is a good idea to have serious causes ruled out.
Then, if the cause is COPD or Asthma, there are medications (usually inhalers) that can help quite a bit.
As for detoxing lungs, the cure is time and no exposure to smoke or other noxious fumes. You can rebuild lung capacity a little at a time, using breathing techniques and gradually increasing the length and intensity of your walks.
https://www.healthline.com/health/how-to-increase-lung-capacity#faq
Have you seen a doctor to rule out serious or treatable causes for the breathlessness?

First, congrats on quitting. I'm quite convinced that nicotine is the most addictive drug out there. I smoked for 50 years, then quit, then started again, finally quit for the last time after being convinced that I'd rather live. Just do like in AA, "one day at a time"! I strongly suspect that you've got emphysema, as I do. You can get inhalers by prescription that will temporarily alleviate the symptoms. Look into pulmonary rehab. Several good routines (FOR FREE) on YouTube. Exercise all you can. Run out of breath, stop & rest, start again. Walk. I've recently started, recommended by a friend, a TCM called Bai He Gu Jin Pian, "Lung Vigor". It's an herbal, lily tuber, licorice root, half a dozen others. I've only been using it for a couple of weeks, so can't really give an evaluation yet. But... DO NOT just sit there!!!