Will persistent cough and cold cause lung hardening? how to cure it, as in lifestyle and diet? :d thanks in advance

Cough and cold: Have to be treated simply because they are annoying. The only problem is that if it is due to a recurrent infection like a viral infection, you can develop bronchiectasis. If it is from allergy, you can treat it symptomatically and as long as no asthma, it does not affect the lung much. Of course some allergies can worsen. Find your allergies and avoid the cause, and treat the symptoms, ask doctor.