Draw a velocity time graph for a ball which is throw vertically upwards from the ground and then it comes back to the ground

We don't draw graphs here. Choose an initial velocity Vo and plot your own.

Y = Vo*t - (g/2) t^2

g is the accelation of gravity (9.8 m/s^2 or 32.2 ft/s^2). Y is the height.

The curve should be an upside down parabola.