If a planet has twice the mass of Earth, its radius would have to be larger by a factor of 2 for the gravitational field strength at the planet’s surface to be the same as on Earth’s surface.
Answers
Of course, it will decrease. From various aspects, we can explain that.
First, we know g = GM/R^2 where G os constant, M is mass and R is radius. From this equation it can easily be daid that gravitational strength(g) will reduce if radius increases. So if you double it gravity will be quarter.
Second, if you increase radius keeping the mass same, that means the density of earth will reduce. It can also be found out from definition of density. Density = Mass/ volume. If we consider earth as a sphere, volume will increase and as a result density eill decrease. From gravity anomalies, we can see that gravity depends on density of objects as well. If density increase, strength of gravity will increase. If density decrease, so, too, gravity. So, from that point also, gravity will decrease.