I have a leak in tiled shower and don't know how to fix it. Do I need to rip all the tile out and how to prevent this from happening.

No, don't rip anything out just yet. Tell us more about the leak, when and how it occurs, where you see water. The leak could be from loose or missing grout, a leak in the shower arm arm, a leak at the shower valve, or in the drain. Tell us more.