As you go through the game you’ll keep gaining level from doing various things, like rescuing survivors and taking pictures. You get the MOST PP from rescuing survivors. You get 500 PP per cultist you kill, 5,000 per Special Force agent. Every 1,000 zombies you get a nice bonus too. Just keep playing over and over until you reach level 50. For a quick way to level up: You need to have unlocked overtime mode, and if you have the megaman buster it’ll be even faster. Head to the warehouse when you start a game in overtime mode, and kill the agents in there (take their guns if you don’t have the mega man buster). Head out through the door to the roof and re-enter the warehouse. If any agent is standing on top of the shelves shoot them, then look down and start shooting the agents on the ground. They won’t shoot back. You’ll level up every 3-5 times you re-enter the warehouse and repeat this.