How do you solve a problem like this: how much force must mr. mcdonald exert to lift a 112 kg object? what would happen if mr. mcdonald would exert more than the the required force to lift the object?

The weight of an object is (mass) x (gravity).

The weight of Mr. McDonald's object is  (112) x (9.8) = 1,097.6 newtons.
(about 247 pounds)

That's the force pulling the object down, because it is near the Earth, and
the Earth and the object are attracting each other with forces of gravity.

In order to move the object away from the center of the Earth ("lift" it), a force greater than 1,097.6 newtons must be applied to it in the other direction ... upwards.

Any force greater than its weight will lift it.  The more the upward force exceeds the minimum of 1,097.6 newtons, the faster Mr. McDonald's object will accelerate upwards.