Hello @luisateresa :)
Nicotine addiction is a tricky one. I have a family member who just won't quit. He has tried many time, but in times of distress he always ends up smoking again. It is a shame!
As for the questions you asked, I believe the first one could be answered by the incentive sensitization model, which states that some pathways in his brain have been modified (the one in the picture above), therefore causing him to want his cigarettes more and more.
The second question can be answered through the cognitive bias model, which states that he has basically a mistaken capacity of reasoning his addiction.
All the best to you my dear :)
I hope your friend can see things clearly and manage to stop smoking!