Was müssen Sie alles tun?
I am confused by alles tun. I know that tun means to do and alles means everything or all.
From this I would arrive at:
What you must do all?
But that doesn’t make sense to me.
Was müssen Sie alles tun?
I am confused by alles tun. I know that tun means to do and alles means everything or all.
From this I would arrive at:
What you must do all?
But that doesn’t make sense to me.
Consider the question without alles.
"Was müssen Sie [alles] tun?"
What ... must ... you (singular formal) ... [everything] ... do?
What must you do?
The alles implies that there are several unnamed things you could potentially list. The person asking expects you to describe some of these things.
Your specific answer depends on the situation, but in general could look like this:
Ich muss [task1 + verb], [task2 + verb], and [task3 + verb].
The answer does not have be a complete, numbered list of literally everything, but a general sample of some of the many things you must do.
This is informal speech. It comes down to "what are all the things you must do?". See this question for reference.