what do i do when my software update do not fonction???? and when my mac is going so crazy, nothing helps?

my mac is acting weird, and all my keys on keyboards do not correspond to any of the normal keyboard keys. it is acting usually messed up, not making program updates anymore, plus so many other problems. it totally blocked firefox and i had to uninstall and re-install it. I am using the key board from my big mac to be able to type anything coherent from my macbook into this message; I just don't know where to start.

please help and advise if you know what this is. went to a apple store, and they tell me it is only the keyboard that needs replacement (200$ min°, but i know it comes from somewhere else. the whole machine is getting a little more messed up everyday. possibe trojan? messed up updates from an apps?

heeeelp!