Joint analysis of the results of the Neutrino-4 experiment and the data of the GALLEX, SAGE and BEST experiments confirms the parameters of neutrino oscillations declared by the Neutrino-4 experiment ($\Delta m_{14}^2= 7.3 \text{eV}^2$ and $\sin^22\theta_{14} \approx 0.36$) and increases the confidence level to $5.8\sigma$. Such a sterile neutrino thermalizes in cosmic plasma, contributes 5% to the energy density of the Universe, and can explain 15-20% of dark matter. It is discussed that the extension of the neutrino model by introducing two more heavy sterile neutrinos in accordance with the number of types of active neutrinos but with very small mixing angles to avoid thermalization will make it possible to explain the large-scale structure of the Universe and bring the contribution of sterile neutrinos to the dark matter of the Universe to the level of 27%. The dynamic process of the dark matter generation, consisting of three right-handed neutrinos, is presented. It is shown that, based on modern astrophysical data on the $^4\text{He}$ abundance, it is impossible to draw a definite conclusion in favor of the model of three or four thermalized neutrinos.