A microscopical theory of electron spectrum and superconductivity in the limit of strong electron correlations within the t-J model is formulated. A constraint of no double occupancy for electron hopping results in a kinematic interaction that induces strong electron-electron coupling by spin and charge fluctuations. A rigorous treatment of the constraint is achieved by applying the Hubbard operator technique for the thermodynamic Green functions. Numerical solution of the self-consistent Dyson equations reveals quasiparticle peaks close to the Fermi surface with an additional broad incoherent band. The interaction also mediates high T(c)s uperconducting pairing which has d-wave symmetry in tetragonal phase and d+s-mixed symmetry in orthorhombic phase for the gap with nodes.