Personally I would suggest Java as the more suitable option for Android development, as it’s generally considered more beginner friendly, and you’ll find a wealth of documentation and examples for Android. It also performs very well on the majority of Android devices, some of which even directly execute Java bytecode.
Either way, you’ll want to head to the Android Developers portal, and get the SDK (or NDK if you choose C++) and tools. The site also provides training tutorials, API guides, a reference, The training material should walk you through correctly setting up and using your tools as well as getting you started with the basics of Android.
Unfortunately no one can provide a real answer to that. Every learns differently and at different speeds, and different people will put in differing amounts of time and effort. You could potentially write your first Android app within a couple of weeks, but it also wouldn’t be unexpected for it to potentially take between 6 and 12 months. Just work at whatever speed you are comfortable and get help if you become stuck.
Alternatively, if you’re not really interested in learning programming you could try some of the tools mentioned in my recent posts “how to make games without programming” and “more ways to make games without programming“. If this is something that interests you, be sure to read the websites carefully so that you’re sure of what capabilities each package offers, and have a good try of the free or trial versions offered before paying any money; these are good products for people who approach them with reasonable expectations, but some of them are reasonably expensive, so you want to be sure you’ll be happy with what you’re getting and are aware of any limitations you might encounter. Making a game is still hard, and these programs are not a shortcut that makes it easy — they’re just an alternative that lets you create the games with minimal or no programming, but still require you to put in lots of work.
Hope that’s helpful!