Battery or Lima broken?

Hello guys, I have the problem that my voltage indicator in the car doesn’t show 14 volts anymore when the engine is running, but only 12V as when the engine is standing. It doesn’t do very well at the moment either. But now I don’t know what that’s all about. Can it be the alternator or the battery? The headlights still work, they are also powered by the battery, right? lg.