It is almost a 10 year old model, things do wear out in time, the keys that have stopped working are in the most used catagory so it is likely that a keyboard replacement is in order, there are good guides on here on how to do that yourself, just needs some patience and a little courage and anyone can do this :) The Batteries are quite easy to change. 2015's are great Macs and some would argue they are amongst the best models apple ever made, I am using one myself!