Cycling - A new hobby

After long 9 years I have started cycling again. Last time I cycled was back in 2005 when I was just out of school. My cycle then was hero devil which I bought for 1750 used for 7 long years and sold for 700. Presently I bought the base version of gear cycle the Hercules Atom (6 gear) as I was afraid I won't get enough time and I would be forced to stop and now after 3 weeks I feel confident that it has become a part of my life I will go a long way with it.

At first I could hardly cycle for 20 min - 3km, and I would soon become out of breathe, I was a bit rusty when I started. Now just after 3 weeks I am able to pedal more than 12km within 40 min which for me is quiet an achievement. I started this mainly because I have small breathing problem and doc asked me to do some physical exercise that would give my lungs some breathing exercise. Don't know why but running/jogging felt too weird so I choose cycling and here I am. The thing that keeps me motivated is the drastic improvement in my breathing problem and the Challenges in the Endomondo app. Hoping to cycle for a long long time and soon to participate in some cycling marathon, just for fun.