Question

a Stone A is dropped from certain height, simultaneously another stone B is fired horizontaly. Which of the two stones will arrive on the ground earlier?

Answer 1

If by ground you mean the same vertical level then they both reach the ground at the same time when you ignore air resistance

The fact that throwing horizontally is just providing velocity in another direction which will not interfere with the vertical side makes the point clear.

The time both reach the ground is

T=((2*h)/g)^0.5

Here h is the height above ground level

g is the acceleration due to gravity 32feet/(sec^2).