The method of germanium and silicon regeneration from waste germanium lenses and photovoltaic cells was successfully verified with the total yield of germanium of above 97 wt %. The preparation of magnesium germanide, magnesium silicide, and their mixtures in an optimized semiopened reactor was investigated in detail. Obtained products were characterized by dispersive Raman spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD), which confirmed high conversion, homogeneity, and crystallinity of prepared products. The measured data, together with data obtained from the literature, served as input parameters for a mathematical model. Subsequent hydrolysis of prepared products to obtain germanium and silicon hydrides was observed by Fourier transform infrared spectroscopy (FTIR) and by gas chromatography mass spectrometry (GC/MS). A successful separation of hydrolysis products to individual hydrides was also performed. Magnesium hydrogen phosphate trihydrate, a desired fertilizer, and the only byproduct of the whole process, was crystallized out from hydrolysis residue with the purity of over 95%.