Thanks for the friend request!

Don't worry about it man, you don't have to be the best to have fun! Anyway, you have to unlock finishers in order to do them... for example, once you beat a level, like the first level, play it on endurance and get 1,000,000 points, and it'll be unlocked. Then, once you do a combo on an enemy, and they turn red, it'll prompt you with a button to press, you press the button, and FINISH HIM!!