reset settings

I've got two issues with my mac.

1. my sound decides to increase every time I press the erase key, also, my three keyboard buttons F7, F8 and F9 don't work.

2. my keyboard buttons don't do what it is expected to do, the Shift key to my right doesn't work at all so I'm forced to use the one on my left.

In closing, I would like to know if it's a keyboard problem on a Desktop problem, and how can it be resolved? Do I need to buy a new Keyboard?