how long does it take to learn parkour?

Depends on your potential and how long you take to bring it out through training, but it's mainly about training. After a few months, if you've already got the right muscle:body-weight ratio, you can have learned all of the basic techniques and even some of the less basic ones. The issue is then to take them to the next level, and you do that through conditioning and constant practicing of techniques, which is all achieve through a careful balance of work and rest. Tricking also takes a little while to learn, and a good deal of time in a gymnastics gym. I've been training for about two years, but I was also one of the people who never really got out of the playground mentality, so I was always doing parkour-like stuff without even knowing about it.

Well it depends if you want to master it probably 2 years. but to learn is easy try vaulting yourself over objects jumping from place to place to get comfortable takes about a month

a long freaking time but if you want to so bad its cool to watch so you shouldnt give up