"Eine Flasche Wein"
why should I say "Eine Flasche Wein" and not "Eine Wein Flasche"? The adjective should be before the noun, no?
"Wein" is not an adjective. "eine Flasche Wein" refers to the amount of wine or the bottle and its content, whereas "eine Weinflasche" refers to the actual bottle (the container).