I’m sorry if someone gave you bad feedback. YOU are actually correct! :-) I am a native English speaker, and I can therefore tell you with absolute certainty that you could answer that request/command many different ways. 1) Sure (very casual) 2) Of course. (Causal but much friendlier) 3) Yes “Yes I will” is more of the type of English you would read in a book. It also doesn’t sound terrible friendly. But that last part is just my opinion.

Both are natural.