Complex sentence: Kurt Selchow, characterized as a "competent administrator" who knew little about cryptography and was preoccupied with the bureaucratic intrigues of the ministry and who left the substantive work to Paschke, Schauffler and Kunze, who ran their subsections affairs as they saw fit.
Split into simpler sentences: Kurt Selchow, characterized as a "competent administrator" who knew little about cryptography. Selchow was preoccupied with the bureaucratic intrigues of the ministry, who left the substantive work to Paschke, Schauffler and Kunze, who ran their subsections affairs as they saw fit.