Is it possible to enhance one's learning ability? I understand that the so-called brain training games like Lumosity doesn't work. But is there any exercise ( mental or physical) that I can do or medicine pills that I can take, that are proven to be able to improve one's learning ability? 

I want to be able to learn fast, and I want to learn so that I can learn even faster!

I am aware that if one does a cognitive task/exercise continuously, one will get better at that task specifically, but this is not what I am looking for. I want the benefits of the exercise to spill over to learning ability. 

Addendum: I found out what I was initially interested to ask: which is whether it is possible to improve one's fluid intelligence.
Interventions which try to make a person 'smarter' in pretty much any sense of the word don't really work. In particular, methods very rarely show any spillover effects whatsoever.

However, what can work is the application of good learning techniques.

Most people trying to learn stuff tend to highlight, reread, summarise, or try fancy mnemonics. These usually don't work very well and are more likely to make you think that you know what you're doing than actually facilitate understanding. 

What people generally don't do but what does work are distributed practice, spaced learning, practice testing.