Your running a 20:12 which is a '1.67' gear ratio. normaly mod have a '1.5' gear ratio which is 18:12. So yeah, that makes it ver high.
You don't need to change your cranks, you can get a bigger cog on the back.
20:14 = '1.43' ratio
20:13 = '1.54' ratio
The bigger cog you have on the back, the lower the gearing.
This is the most inexpensive way of doing it, but you'll need a bit more chain.
Mind you if your a very streety person, and wouldnt mind a bit of speed etc, you could stick with it, pedal gapping would be nice. but normal gapping, and stuff like that will be a bit of a struggle.
:mellow: