Because your pup is still learning what commands and words mean, teaching your pup German commands should be just as easy as teaching him commands in any other language. The primary difference is your own familiarity with the German language, and the extra step of learning the German words that you intend to teach yourself, unless you already speak German.
Which method will work best for your pup will depend on his and your personalities and preferences. If your pup is highly food motivated or sensitive, then 'The Lure Method' will probably work best. If your pup tends to do the behavior that you would like to turn into a command on his own often, then 'The Capture Method' would work well. It will work especially well if that behavior is something that is hard for you to get him to do at other times, such as yawning or licking his lips. If your pup is not very food or toy motivated or he only tends to do a command when you are holding a treat for him to see, then "The Position Method" might work best.
If your pup is not very footd motivated but is toy motivated, then you can also substitute the treats for your pup's favorite toys, and reward him with a quick game with the toy rather than with a treat.