In the frame of the theory of weak turbulence the propagation of electron beams is considered. Using the smallness of quasilinear time transition from kinetic equations to gas-dynamic ones has been done. The obtained gas-dynamic equations are solved for one, two and N monoenergetic beams. It is shown that each beam generally propagates as a beam-plasma structure consisting of electrons and Langmuir waves. Interaction of the structures at their propagation leads to electron exchange and spatial shape changing. Different situations are discussed in dependence on initial beam velocities and densities.