> Energy is conserved in any iteraction.

True. But gravity is a conservative field (again, neglecting radiation), meaning that the energy that goes into raising something against gravity, you can get back by lowering it to the original position again.

> And gravity is not a force. Gravity is the curvature of space-time.

If we're not in "overly pedantic argumentation" mode, then I'd say, go climb some stairs. Feel that? That's a force. But if we are in "overly pedantic argumentation" mode, then yes, gravity is the curvature of space-time in General Relativity. That may not be the final word, though. What is gravity in Loop Quantum Gravity?