"Do I have to be here?"
Translation:Muszę tu być?
because we prefer "tutaj" at the end of sentence. But "muszę tu/tutaj być" is more common. (it is like with pronouns)
Is more common to say 'muszę być tu' or 'muszę tu być' ? Because I wrote the first one and it was considered correct.
"muszę" is "I have to" as in "I must".
"mam" is simply "I have".
You can also use "mam" as a modal verb: "Mam tu być" is closer to "I am supposed to be here", I'd say. I don't think we teach it.