the behavior of gravity, is well-known from Newton.
The cause of gravity is still not quite understood, Einstein's relativity is as close as we've gotten so far.
That does not mean we can't use gravity, to explain what we observe, and how to use it?
We use it to put satellites in orbit, we use it to send, probes to orbit around Saturn,
we use it to put probes on Mars,
we use it to put probes eo do flybys of the outer planets.
We have used it to put man on the moon.
But enough of that.
The mass of the earth, has a gravitational pull to its center. It appears that you have no understanding of this. As you deny it.
The earth rotates, making one rotation in 24 hours.( Exact numbers are not required for that understanding) this giving you a day night cycle.
The earth orbits the sun in 365 days, you ask how we know this, it is the change of the constellations in the night sky. In every four years, we make an adjustment of a day to have the right consolation facing us again.( Leap year ).
We now get more complex, by adding the moon, to this model.
It is said the moon orbits the earth, this is not quite true, as the earth moon pair, orbit their common gravitational center point. But the moon being smaller of the pair, is the one considered to be orbiting, and approximately in 29 days. The center point, is also within the surface of the earth, and moves in line with the, orbit of the moon, and is the cause of lunar tides. These are the observation of the earth moon orbiting the sun.
I do not know how to explain it to you, any better that I just have.