To speak is to talk. Often used with languages.
There are some people speaking English outside. I’d like to speak to Bill.
To speak up is to talk louder.
I can’t hear you. Can you speak up?
Here, the preposition UP is used literally, like turn the volume UP.
To speak out is usually used about taking a stand on some issue, like a political, social, ethical issue.
Activists speak out against the mistreatment of women and minorities.
Speak out against is a common collocation. Speaking out is a public declaration of your position.