Keyboard not working properly ):

Hello,
my built in keyboard is giving me headaches. Does anyone know why and how to fix it? Currently i'm using a plug in keyboard. When i type a certain word, it will turn out to be three words. For instance, when i type 'd' or 'f' or 's' ,it will become 'dfs' or when i type b -> b,. , w->erw , e->erw , r->erw ,t->iot , 2->234, 3->234 , 4-> 234 , l-> ?¬ , o ->io , i->io , x-> cvx , c-> cvx , v->cvx and my delete is not working. But some words is normal like a, h, j, p, u, y, z , n, m. If it cant be fixed, how much do you think to fix or change the built-in keyboard on my mac? HELP PLSSSSSSS.