Why do all the stars and planets of a galaxy spins in a circular way around it’s center?

Not a very 'therapy' based question XD.But as you asked, the spin of a galaxy, but more like the spin of what is in it is based on centripetal force. If you spin a bucket of water fast in a circle above your head, the water does not pour out, as the 'g-force' causes a pull to the outside of the spin. In the same way the pull of a blackhole in the center causes this spin to begin and the force is equal to the force pulling in, thus the object (in this case a planet etc.) would spin in an oblong shape around in an orbital, and we can tell that the force of spin is equal or greater than the blackholes inwards drag, as if it was not, It would collapse into the blackhole and become spaghettified etc. Thats as basic as I can make it! So it spins with enough force to never properly reach the black hole, but maintain a circular motion, in the same way the moon revolves around the Earth, and the Earth around the Sun. This explains the phenomena better https://www.youtube.com/watch?v=M7eCBr0JkgE . There is also theories based on dark matter interaction, which is thought to help the spin and to help stop collapsing into the supermassive blackhole at the center.@Stormwolf6 | A-level Physics

This is something more suited to Google, but there is something along the lines of a black hole or some kind of mass that everything does gravitate around. I don't remember exactly what it is, it's been a while seen I watched that documentary. :P

(http://www.eso.org/public/science/gc/) There you go, there is a supermassive black hole. You were right.