After you die, you can do 3 things. The first thing is that you can train at King Yama's, it will be just as if you were training in the living world. The second thing you can do is travel to King Kai's and train there, your traveling time will be depended on your speed. The third and final option is that you can just sit back somewhere in the dead dimension and what for someone to wish you back to life. Remember, if you choose to go to King Kai's, you have to make me laugh just like the Z characters made him laugh. Once your at King Kai's Planet, your stats will increase twice as fast through training sessions. When training anywhere in the dead dimension, you have to train under the same conditions as if you were alive. If your thinking what happens to your items while your dead, then don't worry about it cause you will still have them when you come back to life.