Hiya Diana. Yes of course we can say that in English but it depends on the context. You will need to tell us the context and what specific thing you want to say.

"What happens?" means "what always happens?"

For example, here is a question: "if you are late for class, what happens?" Answer: "the teacher is angry." This means "always / usually". It means you're talking about something that's usually / always the same way.

The next one is different. If you say "what does happen?" it means that somebody has just told you what does not happen and now you want to ask what does happen.

For example  "if you are late for class, what happens? Does the teacher cry?"

"No, that does not happen."

"Oh, I see. Well, what does happen?"