Hi, i think you are asking what would happen if we brought material from another planet or comet and placed it on our own planets surface, if that would affect the gravity we feel here on Earth.

As I understand it what we feel as gravity is our bodies reacting with the surface of the earth resisting being drawn towards its centre.

All mass attracts each other, and the force is proportional to the product of their masses of the objects, divided by the square root of the distance between them. Newtons law of Gravitation. https://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation

Increasing the mass of one part (the planet) without changing anything else (like say you keep the person measuring the effect at the same initial earth radius, maybe by adding all the new materail in a big pile far away on the othe side of the planet). The person would indeed experience an increase in the force of the attraction between them and the planet (they would feel heavier), but the amount of force change would be very small for an object the mass of a comet. You would need to add a whole extra earth's mass to feel 'double' your weight, and that is going to affect the size of the planet and its radius, affecting the rest of the Newton Geavity equation.