Question

if gravity pulls you down towards the centre of the Earth with a force of 500n how much upward force does the ground exert on you​

Answer 1

If gravity pulls you down toward the center of Earth with a force of 500 N, how much upward force does the ground exert on you? You would get 500N upward force. The net force would be 15 N because it's going in the same direction you plus 10+5=15.

Answer 2

If you're standing still on the ground, there's no net force operating on your body:

Gravity has a DOWN force of 500 N on you.

You must have a 500 N UP force acting on your body to achieve zero net force.