So you could delete your PhysicalSurface, Gloss/Specular Conver, and Specular nodes, and instead add the Cycles and PrincipledBDSF nodes as Ghostship suggested. With your Diffuse plugged into the PrincipledBDSF node. That is an admirably simple setup.

That said, looking at your PhysicalSurface node, if you want a shiny surface while using this setup, the obvious change would be to reduce the Roughness setting. I don't know about the Gloss/Specular Converter to speculate about that part, but lower roughness will generally increase shininess. For even more shininess, you could increase the Metallic setting.