I'm no expert on German, but that looks fine to me. All the words are correct but I'm not entirely sure about the cases/case endings. It looks pretty good to me though. Sorry if I couldn't be a better help :)
20: what are you doing after school?
21: what are you doing on the weekend?
22: what do you like to eat? (generally)
23: what don’t you like to eat? (generally)
24:what is your favorite subject?
25:which subject do you find boring?
26: what do you like to drink? (generally)
27: which subjects do you have this semester?
28: at what time do you have german?
29: do you like natural science?
30: what do you have in your school bag every day?
i hope i could help you :)
