Is There a Black Hole at the Center of the Milky Way?

Could a bigger black hole at the center of the galaxy explain how all the stars are moving around the galaxy? Or does it have to be something like dark matter? Is th sort of three answers, two knows, and then maybe yes. We can measure the mass of black holes by looking at the movement of stars near it. And every star, its motion, tells you about how much mass is in a sphere that's closer to or further away than it should be. So what we need is dark matter to explain all of those different velocities stars closer to the center and stars further from the center.