Co3Sn2S2 is a metallic ferromagnet with Tc = 177 K, which crystallizes in a shandite-type structure. Below the Curie temperature its electronic structure forms a half-metal state. Such systems attract much scientific attention due to its possible applications in spintronics. However, they are also interesting from the fundamental point of view. There are two kinds of magnetic collective excitations: transverse modes, which are described by the Heisenberg-like hamiltonian, and longitudinal modes. According to our theoretical estimations, these modes have gaps of different order in the proposed system. Previously, it was shown that the magnetism in Co3Sn2S2 can be suppressed by doping it with indium or iron, thereby initiate quantum phase transition. So, it is justified to rise a question about the role of the different kinds of magnetic excitations and how they respond on doping.