"From what do you want to make the soup?" can this be said in English?
Yes, it can, though the translation given above is more commonly used.
Got it! Thank you.
I vote for Lucia's version. The main issue here is: From what?, so keeping from near what makes more sense then putting the from so far after the what.
"From what do you want to make the soup?" also is accepted.
Still, in English the other version would rather be used "What do you want to make the soup from?" Having the "from" at the beginning sounds weird.
"From what do you want to make this soup?" is not accepted. Isn't the and this interchangeable in Czech since there isn't a definite article?
No, they are not. Yo have "tu polévku", "this soup" would be "tuto polévku" or "tuhle polévku".