Jawohl?
Rubbish, I think, the Germans were a long way off making any kind of nuclear weapon - they had the theory worked out, but towards the end of the war the scientists in charge were more interested in surrendering to the US/UK forces (as opposed to the Soviets) than helping Hitler out - they'd realised by then that what they were working on wouldn't do Germany any good at all.
Karlsch claims the bomb was detonated on March 3rd, 1945
Germany surrendered on May 8th, 1945
The first US atomic test was on July 16th, 1945
So the Germans managed to beat the USA despite heavy bombing, the disintegration of their command structure and the removal of their only heavy water supplies (by an extremely brave Norwegian commando raid) and having a fraction of the resources. Yeah, right. Building an A-Bomb even now is something that takes years and lots of $$$, let alone building one with no blueprints to go on while being bombed and with dwindling resources.
The man has a book out. Nuff said.
Spiegel article (English)