Is these correct?
Can I say: "What nationality are you or what is your nationality?"
Is it equals: "Are you married and what is your marital status?"
What do you do and what is your profession?
How long do you work on this job?

Question

Answer

For the nationality one, both are equally good.

"Are you married?" is much more common than "What's your marital status?", which is really only used on job applications and things like that.

Both are good. "What do you do (for a living)?" is less formal than "What's your profession?"

"How long have you worked at this job?" OR "How long have you been working at this job?"

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