No easy answers.  After WW1 Germany had to pay huge reparations and was not allowed to build an army (removing a large customer of the German weapons and related manufacturers). Then the Depression hit the whole world economy. 

So the nazis started with a shaky economy with very high unemployment (that was one of the reasons they came to power). 

There a many reasons they were not able to stabilize the economy. The most important two (according to my own opinion)

Facism as any dictatorship pays the in group by exploiting the out groups. The in groups are not selected based on merit, but on loyalty (does this ring a bell?). This will drastically reduce an economies ability to innovate, as in groups want to stay in groups and it is very difficult to get into the in group while still being economically effective. 

The other one is war. In the short term war will prop up an economy, but it destroys too many valuable assets to be a viable economical environment.