Any advice? i have been smoke for 4 months already. i smoke 3-4 cigerettes per day. if i quit now, can my lung recover to its normal state?

Yes: after only 4 months of smoking and only a few cigarettes per day, the odds are very good that no long-term damage has yet been done, and that your lungs will fully recover. You may find an increased cough after quitting, because your respiratory tract is trying to rid itself of a lot of accumulated junk, and thats how it does it. This is normal but may last a few weeks. Congrats and quitting.