"Do" actually has at least a few dozen dictionary meanings, but you shouldn't feel that these are the only ones possible. "Do" is one of those English verbs (like "get") that can be used to make up new phrases, the meaning of which you are expected to understand from the context. For example,
Roger doesn't do lunch.
Even if you've never heard this expression before, or you can't find anything related in the dictionary, you can still understand from context that the speaker means that Roger ordinarily does not eat lunch.
Another possible variation is:
Roger doesn't do lunch breaks.
This means that Roger either doesn't personally take a lunch break, or he doesn't believe the people he manages should take lunch breaks. Again, in context, the meaning should be apparent.
For example, suppose you are talking to a professional chef, and you suggest you two get something to eat at McDonald's. The chef replies haughtily:
I don't do fast food.
meaning she strongly dislikes eating a fast-food restaurants, and, presumably, prefers restaurants that take their time.
On the other hand, suppose she's cooking for you, and you suggest that you don't have a lot of time. She might respond:
I'm sorry, I don't do fast food
meaning that when she prepares food, she prefers to take her time, not rush.
Again, the point is that "do" has an extraordinary range of possible meanings, and you shouldn't limit it to only those you find in a dictionary. Moreover you have to pay attention to context, since the expected meaning might be changed to something else, for humorous effect.
For example, since "do" can also mean "have sex with", I can make your example a little more risque:
A: Jack did French at school but he didn't do German.
B: So he can speak French?
A: No, not a word. I mean he had sex with a French schoolmate but he never managed to get with that German he fancied.