The German's have 2 kinds of cannons, and they both have their own play type.

the MG FF/M

• accurate
  
• low firing speed
  
• less damage due to the low firing speed and velocity
  
• low range

So for the MG FF/M i recommend using anti Air or omni-purpose rounds combined with stealth rounds for the 7.92mm because aiming will get ALOT easier when no straight green beam of brightness comes out of your plane and messes up your aim.

the Mg 151

• high firing speed
  
• low accuracy due to the high fire rate
  
• greater damage due to the high fire rate
  
• more spread MEANS better for head-ons
  
• also low range

for the Mg 151 I recommend stealth and anti air (only stealth if you have more than 2 MG 151's because the white beam that comes when you fire all your cannons could mess up your aim so it's better to take stealth rounds for the 7.92 and one pair of the MG 151's/MG FF/M and for the other 2 cannons I recommend to take anti-air rounds.)

here you can see the spread of the MG 151. watch at fullscreen to see it correctly


and here you can see the accuracy and low range of the MG FF/M

The Fw 190 is well known german interceptor we'll cover the playstyle and weapons of the A-1 and the A-4 (because I only have these 2 unlocked :P)

The A-1/4

• it's very fast it can reach up to 676 Km/h
  
• It can't resist alot of damage a yak 9 or a spitfire (as I like to call it: ♥♥♥♥♥♥♥♥) can easily kill you without any trouble whats so ever!
  
• not very manoeuvrable so try to stay out of dogfights or turnfights!
  
• one of the BEST boom&Zoom planes out there so always have an altitude advantage over the enemy you want to shoot down
  
• the 20mm don't have much ammo so if you perhaps shoot 2-3 enemy's down you'll have to reload. When you're reloading the best tactic to NOT die is to stay low and fly in direction of your team's spawn so they can protect you while you are reloading

the Bf 109 is a german fighter obiously but many prefer to the Fw but the Bf 109 also has it's potential's! here we will be covering the F-1 ( because that's the only one i mainly use and have more experience with it so sry :/)


The Bf 109 F-1

• again: not very manoeuvrable so stay out of dogfight's and turnfight's
  
• VERY easy to shoot down
  
• good for Boom&Zoom
  
• only has 1 20mm MG FF/M, so make you're shoots count!

here you only need one thing to know don't JUST DON'T go in a dogfight with these planes otherwise they will: outturn you, kill you instantly, or gangbang you.

but there is a way to get rid of those pesky yak's , ♥♥♥♥♥♥♥♥'s and hurricane's
wait until they want to turn their plane and show you their weak top part of the plane where the pilot is sitting, try to snipe the pilot and BOOM no more pesky yak's, ♥♥♥♥♥♥♥♥'s or hurricane's only pilot-less plane's Gliding slowly to their death.

for the FW 190 A-1 I recommend:
7.92mm=stealth
MG FF/M=anti air


for the FW 190 A-4 I recommend:

7.92mm=stealth
MG FF/M=anti air or omni-purpose
MG 151=stealth


for the Bf 109 F-1 I recommend:

7.92mm=stealth
MG FF/M=anti air

obiously in a german plane you not have the maneuverability of an ♥♥♥♥♥♥♥♥ or an hurricane so dogfight's and turnfight's aren't the places you should supposed to be. where you should be is far away from big group's of enemy's , go for the alone guys they don't stand a chance when you come out of nowhere and feed them with your MG fire.


you might end up like this if you go in a dogfight:

well head on's aren't very effective due to the weak structure of the FW 190 and the BF 109 they have great cannon's of course but if you want to stay alive you better avoid head on's especially with british planes and american planes.

BUT
there are still some technique's to win a head on, if you are a skilled pilot and know what you are doing. When you make an head on with perhaps and ♥♥♥♥♥♥♥♥ shoot at 0.80-0.90 km and immediately turn away that won't give the enemy the opportunity to shoot his (OP) 20mm at you and kill you instantly.

I'm german so english is not my first language if there are some misspells i'm sorry

but anyways I hope this helped decreasing your death rate

GOOD LUCK