It is a slang term. To "get up" with someone is another way of saying I'll see you/talk to you later. For instance if you told a friend that you were hanging out with that you need to leave to go study they might reply, " Ok, get up with me later." Meaning you should call them/contact them when you are finished studying.

Wow, Nique, I didn't even know that meaning! I think it can depend on where your friend is from; in British English, my native language, it means to me to stand up or move. For example, if you are sat in a chair, you can be told to get up, so you are standing or moving around. As a slang noun, it can also refer to clothing; for example "you should see her in that get-up" but it has negative connotations.

It may also mean " to stand up on feet "

It just means you are "down". Don't stay down, get up.