Student or Learner
Is it correct to say "do wonderful"? For example, the stuff are doing wonderful.
It's not correct, but it's he sort of thing you will hear colloquially- using adjectives instead of adverbs is common enough, but would be marked wrong in an exam and would look out of place in formal language.
Are you sure you meant "stuff" or is "staff" perhaps the word you were looking for?
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.