How can I thank the secretary?

Do your job well, this is the first. Second, it is certain to express gratitude. If you say that your secretary will retire just because she has only three or four years, then you are a bit snobbish! Third, you don't have to give him something expensive. The most important thing is to get to know him and talk about what he is interested in. Maybe he thinks he has found a bosom friend! Isn't this also a kind of gratitude? The most important thing for a person is to know that he is valuable, to reflect his own value, and to speak more good words about him in the future, not afraid that good words will not reach his ears!