How to form questions?

Question

I started learning French (A1 French learner) and I am confused with forming questions in French. For example I want to ask what is your profession?

Quelle est ton/votre profession?

I know that because profession is feminine we use quelle. Are we using ton/votre to show the possession of whom we are talking to the profession? Is this correct:

Quelle profession est tu?

If it's not correct, why can we say quel age as tu? Question word+ age+ avoir verb + subject? and not apply the same structure when asking about some ones profession?

Answer 1

Quelle est votre profession ? is fine when you use vous with the person you talk to but otherwise, that should be Quelle est ta profession ? profession being a feminine word.

Unlike English, possessive adjectives must agree not only with the person possessing (my, your, his/her, our, your, their) but also with the thing being possessed (mon/ma/mes, ton/ta/tes, son/sa/ses, notre/nos, votre/vos, leur/leurs).

Quelle profession est tu ? is odd, you wouldn't ask that to a person but rather to a profession (What profession are you?) You would say instead Quelle profession exerces-tu ?

Note that in actual conversation, you are more likely to hear questions like Tu fais quoi dans la vie ? or Vous faites quoi comme métier ?

We can ask Quel age as-tu ? because you kind of "own" an age (literally: What age have you?) this is not the same sentence as "How old are you?" which would be literally "Combien vieux est-tu ?" (not idiomatic)