bring something down means make unhappy (e.g. This sad music is bringing me down.)
bring something up means start talking (e.g. My mother walks out of the room when my father brings up sports.)
bring something up means vomit (e.g. He drank so much that he brought his dinner up in the toilet.)
bring up a topic etc. means introduce it in a conversation (e.g. I don’t want to hear any more about this matter. Please don’t bring it up again)
bring up means raise, look after a child (e.g. Her parents died when she was a child and she was brought up by her grandparents)