Why can we say both "I am studying at the University" or "I study at the University" but when we say " I am learning about wine" we cannot say "I learn about wine" ?
Sure you can. If I ask, "What do you do at the university," if you are studying oenology, you can reply, "I learn about wine." This response describes a general (albeit not infinite) state, as opposed to one occurring over a more or less fixed or set time. In the former instance, the simple present is appropriate, and in the latter, the present progressive is appropriate. (More information: https://www.ego4u.com/en/cram-up/grammar/simpre-prepro).