Hello Lola, let me try to answer your question: "¿Con quiénes va el joven al instituto?" and "¿Con quiénes va al instituto el joven?" are BOTH well-formed in Spanish, but there is a difference in end-focus and the first construction sounds a bit more natural than the second. In "¿Con quiénes va el joven al instituto?", it is "al instituto" that is in end-focus position, whereas in "¿Con quiénes va al instituto el joven?" the end-focus position is occupied by the subject, "el joven". However, only relatively long (informationally "important") constituents sound well in end-focus position, and "el joven" is a bit too short. That is what makes the second construction less natural than the first. If the subject were longer, for example, "el joven con el que sale tu hija", then "¿Con quién va al instituto el joven con el que sale tu hija?" would sound MUCH BETTER than "¿*Con quién va el joven con el que sale tu hija al instituto?" (which is difficult to process and, in fact, barely understandable). I hope the concept of "end-focus" is familiar to you from English grammar. In Spanish, as in English, we have TWO focus positions, one at the beginning of the clause for "WH-interrogatives" (in Spanish: "quiénes", "con quiénes", "por qué", "qué", "cuándo", etc.), and the default end-focus position, at the end of the predicate. [Chinese is very different in this respect. You do not have initial focus, because your interrogatives (e.g., "shénme", "duo1shao3", etc.) are NOT fronted (cf. "nín yào shénme" > literally: "What do you desire?"), nor systematic end-focus, either, because optional prepositional phrases that are obviously in focus must still precede the verb, which often leaves an unfocused verb last in the Chinese clause]. Best, :-)

> "i thought it's va + a tightly, is it wrong?" Yes it is wrong!

se le agrega el articulo (el, ella, ellos, ellas nosotros, nosotras, ustedes) para saber el sexo del sujeto (JOVEN) en cambio si vos escribis con quienes va carlos al instituto no necesitas el articulo porque estas aclarando el sexo del sujeto

cuando tienes la preposición "a" seguida del artículo "el" siempre se convierte en "al" en este caso sería "el joven va a el instituto" por la regla que he comentado se convierte en "el joven va al instituto"

It's not. It's va + a: ¿Con quiénes VA el joven AL instituto?