What makes the sun float? Maybe the whole solar system is actually sinking

If you thing about it. All thing's sink. So why is the sun any differnet. It has to sink. Were's it going?

An answer said that the whole solar system is being attracted to the centre of the gravity is theoritically not true, cause all objects are moving away from each other. There is a giant balckhole, supposed to be in Milky Way, but it's force is too tiny to stop other repulsive forces at work, thought to have initiated from the big bang.

All things do not sink (if by sink, you mean fall). If there is a presence of a strong gravitational force, then gravity will play its role. On Earth, for example, if you drop a bottle of water, it falls to the ground. In our solar system, if you let go of a bottle of water, it doesn't fall anywhere, it just stays in orbit with the nearest body with a significant enough gravitational force. The sun doesn't sink anywhere. It orbits the center of the Milky Way. It just happens to be on a certain plane in space. It doesn't fall.

I hope this is a joke, but I'll answer it anyway.

The sun is not "floating". It does not sink to the floor as a ball would on Earth if you let go of it. The sun is gravitationally bound to a supermassive black hole at the center of the milky way. It is accelerating in a circular motion around the center. Since the Earth is gravitationally bound to the Sun, it follows the same trajectory around the center of the milky way. As a result, the sun doesn't appear to move relative to the Earth (though the Earth moves relative to the sun) so I guess that's what gives the appearance that it's "floating".

Imagine having a rubber ball attached to the end of a string, then waving it around your head like a lasso. Notice how the ball doesn't sink. It is the exact same force that keeps the sun from "sinking".