What really a charge is apart from saying its a fundamental quantity. I mean IF in case of gravity, its curvature of spacetime due to mass so just like that can anyone explain how charge like properties come in place
in case of gravity, its curvature of spacetime due to mass
technically to the stress-energy tensor so energy density, energy flux, pressure, shear stress, momentum density, and momentum flux. But yes, for a stationary object with no internal stored / binding energy, it's just the mass. And we could also ask -- what is mass exactly? Elementary particles with same sizes have vastly different masses, so, like charge, it must be something "instrinsic" (... or at least its coupling to the Higgs field).
A charge (not electrical) is the generator of continuous symmetry. As per Noether's theorem, a continuous symmetry implies the existence of a conserved current (not necessarily electrical).
In the specific case of electrical charge, it is the generator of the U(1) symmetry associated with electromagnetism (QED). The conserved current is electrical current.