What is the plot for Dragon Ball Z

It is about a Saiyan named Goku who was sent to earth from planet vegeta to kill the inhabitants, but is hit on the head and becomes good, so he is found by a guy named Gohan who raises him and dies, Where Goku grows up and meets bulma and they go to find dragon balls, they meet many friends and have epic battles but goku grows up and gets married and has a son now his brother comes to earth and tells him that he is not a human but instead a saiyan from planet Vegeta and he must fight his brother and other warriors to save the universe using transformations and Martial arts and blast