hi! the example that iago deceives othello is good to start with, but remember that answering the question is key - try to focus on what this shows about othello's character. start with a statement about one of othello's main traits, and then your example would be how this is shown in the play.
your statement, for example, could be that othello's fatal flaw, or hamartia, is jealousy, and then your example would be that he easily believes iago's lies about desdemona being unfaithful. something else you could say is that othello places trust in the wrong people. then, you could say that he trusts iago and distrusts desdemona as examples.
also, remember to include techniques in your examples! if you write about how othello trusts iago, you could say that he constantly calls iago 'honest', which is an epithet. the epithet emphasises othello's undying trust in iago because of how repetitive it is (you could also add that this is dramatic irony, because the audience knows that iago is deceiving othello - the effect of this is that othello comes across as rather gullible).
i hope this helped! let me know if you need any more points on structure
