Why Earth is not falling up or down in Space ?

There is no "up" or "down" in space, except in the sense that "down" is towards some centre of mass (which can be a moon, planet, or star) and "up" is away from that centre of mass. Earth is falling towards the Sun, but has enough momentum left over from its origin in the solar nebula to result in a stable elliptical orbit.

In space there is no up or down.

And even here, "down" in the US is not the same direction as "down" in Australia. Local "down" on earth is always towards the centre of the planet, no matter where you are.

The gravity of the sun is trying to pull the earth "down" towards the sun, but the earth is orbiting around the sun, so centrifugal force tends to make it fly "up" away from the sun.

The sun's gravity "down" and centrifugal force "up" balance each other, so the earth stays the same distance from the sun and keeps moving on an (almost) circular orbit.

There is no up and down in space. Gravity works by pulling everything to one area. Asteroids also orbit stuff in space, if there is nothing to orbit it will move in a straight line.

There is no up or down in space. Gravity works by pulling everything to a centre of mass such as the Earth's core or the core of the sun.

It is falling, the Earth falls around the Sun - that's what gravity is about and an orbit can be seen as eternally falling to and missing.

The Earth falls around the Sun, the Sun falls around the centre of the Galaxy.

We know up and down by the gravitational force of the nearest large mass (namely the Earth). We are also not in freefall like objects in space, so you cannot apply what you experience here, out in space as well. Most of the universe that exists beyond our experience is completely unintuitive to us.

Because there is no up or down in space!

Conventional wisdom and Newtonian Mechanics are two blocks in your thinking and comprehension.