A first principles based density functional theory (DFT) has been employed to doped free standing (FS) germanene mono-layer by arsenic (As) and gallium (Ga). It has been revealed that electronic, magnetic and optical properties can be tailored by either (a) type, (b) concentration and (c) choosing specific sites of substitutional doping elements or suitable combinations of them. As a result, one can tune the splitting of Dirac cones at or near Dirac K point by proper doping. In particular, similar type doped structures indicate transition from semi-metallic to metallic region. Besides, induced magnetism for double doping in FS germanene can be traced back to the 4p level electrons in spin-polarized projected density of states. Optical property analysis predicts that values of static dielectric constant (61(0)) and refractive index (n(0)) are enhanced significantly than pristine layer by proper doping in case of parallel polarization. Optical conductivity study elucidates the fact that, height of maximum peak is amplified by 5.50% than pristine system for double Ga doping at non-equivalent site. We strongly believe that this investigation of electronic, optical and magnetic properties of doped germanene nanosheet might be useful as a powerful tool for next generation germanene based nano-technology. (C) 2017 Elsevier B.V. All rights reserved.