Note that there is no real right and wrong way to play Germany but I think the most important thing is to
FOCUS
Go all in with army or navy focus and all in navy around 41 or so and your BB,BC, or SHBB can rip apart the allied navy. Airforce is kinda optional as Germany as it is hard to keep up with the advance in the USSR and USA. You should have the war all but won in 43 or so with mopping up operations. That being said a heavy focus on the airforce will also let you rip through the AI very easily. The main advantage of using say armr and inf is you don't need to research all of the other types of infantry and it is a similar deal with BC+CL fleets as you don't have to research CA,DD, CVL or even subs. Convoy raiding works but it is slow and mostly a waste of time. I use it to train up my rear admirals to take command of my capital fleets. Rockets, strategic bombers,paratroops, transport planes and carriers are a bit pointless as Germany but they work OK if you focus on them. Germany usually has around 4-500 IC so can do anything it wants for the most part.
FOCUS
Go all in with army or navy focus and all in navy around 41 or so and your BB,BC, or SHBB can rip apart the allied navy. Airforce is kinda optional as Germany as it is hard to keep up with the advance in the USSR and USA. You should have the war all but won in 43 or so with mopping up operations. That being said a heavy focus on the airforce will also let you rip through the AI very easily. The main advantage of using say armr and inf is you don't need to research all of the other types of infantry and it is a similar deal with BC+CL fleets as you don't have to research CA,DD, CVL or even subs. Convoy raiding works but it is slow and mostly a waste of time. I use it to train up my rear admirals to take command of my capital fleets. Rockets, strategic bombers,paratroops, transport planes and carriers are a bit pointless as Germany but they work OK if you focus on them. Germany usually has around 4-500 IC so can do anything it wants for the most part.