How do you ask who are you in German?

Answer 1

Formal : "Wie heißen Sie?" or "Wie ist Ihr Name?". Though that could sound a bit clumsy or harsh. More polite would be "Darf ich erfahren, wie Sie heißen?" or "Dürfte ich Ihren Namen erfahren?" ("May I hear your name?"). But then again, in some situations these questions could sound sarcastical. In the German language it's often an extremely fine line between being polite and being sarcastical, in my opinion.

It might be safer to introduce yourself first and then let the other person say his/her name.

Informal: "Wie heißt du?" or "Wie ist dein Name?".

If someone is older than you, it doesn't automatically mean that you have to use the formal adressing. Actually, youths are always adressed with Du (informal). So, you can say "Du" to everyone before the mid-twenties, or even before the mid-thirties. For instance, if you ask someone the way and you think that they are not older than 30/35, you would ask "Entschuldigung, kannst du mir sagen, wie ich zum Bahnhof komme?" (Excuse me, can you tell me how to get to the train station?).

In working life it's different again. A boss is always adressed "Sie" (formal), unless he/she offers the "Du" (informal adressing) - even if the boss is younger than you.

Also, in some schools, there is a concept which allows the pupils to say "Du" to the teachers.

So, it really depends...

I would say, if you are not sure, just wait and see what the other person is doing/how she/he is talking to you.

Examples:

If you have a chat with an older lady in the bus and she guesses you are not older than 17/18, she will probably say "Du" to you. But you will address her with "Sie", anyway. If she is a nice and warm person, she could say "Du kannst aber auch ruhig Du sagen" ("Just say Du, too"). Mostly, that won't happen, but however, it's possible.

If someone, who is not considerably older than you, uses the informal adressing, you can do the same. In professional life you should always be adressed with "Sie". If someone says "Du" instead, it's often a signal for you to say "Du" to the person, too.

Of course, there are exceptions - as always...

Answer 2

Who is that = wer ist das

who are you (informal, singular)= wer bist du

who are you (informal, plural)= wer seid ihr

who are you (formal) = wer sind Sie

who is he = wer ist er

who is she =- wer ist sie

who is there = wer ist da

who is it = wer ist es

Answer 3

Ich heisse [your name].

or

Ich bin [your name].

Answer 4

Who are you = Wer sind Sie (formal)

Who are you = Wer bist du (informal, singular)

Who are you = Wer seid ihr (informal, plural)