Later, Timm transitioned to professional boxing and was hired by the promotional company Universum Box Promotion. He worked with boxers such as Jurgen Braehmer, Sergei Dzindziruk, Andriy Kotelnik, Vladimir Sidorenko, Ruslan Chagaev, Felix Sturm, Juan Carlos Gomez — who sooner or later became world champions — and many others.
When Universum fell from the top ranks among boxing promotional companies, Timm returned to the Schwerin "Traktor" and amateur boxing, as well as working with the German national team.
Timm, along with Fritz Sdunek, Ulli Wegner, and Torsten Schmitz, was one of the leading coaches of the golden era of German boxing, when Universum and Sauerland Event produced one world champion after another.