Do NOT buy a "K+DCAN" cable alone. You need the physical 20-pin round plug. If your Diag Head does not have a 20-pin male connector, you cannot diagnose an E36 or E39.
BMW INPA/DIS/SSS Diagnostic Kit is a comprehensive legacy software suite used for deep-level diagnostics, coding, and programming of BMW vehicles, primarily for E-series models from the late 1980s to roughly 2017. While powerful, modern users often find it complex to set up compared to newer tools like pss-autosoft.net Core Software Components bmw inpa 301 dis sss and diag head with instuctions link