There are many ways to get experience points in The Outer Worlds, and these will eventually lead you to level up. But have you wondered what the max level in The Outer Worlds really is? As of right after the launch of the game, the max level is set to level 30. This number is a lot lower than a lot of people had expected, but the estimated time for a regular player to reach level 30 is somewhere between 40 and 50 hours, so it will still take you a very long time.
There is a possibility that future DLC or content updates will increase the max level in The Outer Worlds, but for now it is level 30. So enjoy the game, and good luck with hitting the level cap.