As I am unable to read German I am unable to fully give details for this. Title appears to be “Mord Auf Bestellung” “Geheimauftrag fur John Drake 1” (Secret Task for John Drake 1) by Ralph Smart. While this was defiantly produced in the sixties I am unable to find a publication date inside. It would however appear that it was translated from English by Wolfgang Lohmann and the publisher is possibly Signum Taschenbucher. From studying the back cover it looks like there may have been a second title in this series “Gasthof zum Galgen” but unsure.