Coming from the Slavic tongue (polish included) we say dorze when replying to "how are you" (adverb) dobra is like when "The girl is GOOD". Here it's dobra because it's a feminine adjective whereas if it were a man that was good, it would be masculine, dobry. This also applies to either f. Or m. Objects. Dobre can be more complex. It can be adverb like dorze OR an object that is good or does well... etc... kinda hard to explain...
Because, in English, the phrase: "Fine, thank you" is just a polite answer
to the greeting, not to the question about condition or details of your health.
In Polish, the greeting "How are you? - Jak się masz?" is quite often "an invitation" to a little chat, often involving health, work, and other issues...
I had assumed that this was probably the anwer to 'Jak się masz?' If I'm asked 'How are you?' in English I would probably say 'Fine, thank you' or 'Well, thank you' to mean more or less the same thing, so I assumed that the same would go for 'Dobrze, dziękuję'. It seemed to work that way when Polish people asked how I was when I was working in Poland, but I'd be the first to admit my Polish was never that great, so I could be wrong!
http://popolskupopolsce.edu.pl/lekcja/1/MAZOWIECKIE - this page is quite good in showing the sounds. See both parts 1 and 2. "ch" is pronounced strangely in my opinion and it should be identical to "h".
"cz" is the first sound of "Czech".
"ć"... well, it's hard to explain the alveolo-palatal sounds, especially that I'm bad with phonetics... maybe see here: https://en.wikipedia.org/wiki/%C4%86
"dz" is roughly the last sound of "woods".
"ź" (with an 'accent') - see here: https://en.wikipedia.org/wiki/%C5%B9
"ż" and "rz" are the same sound, roughly the last sound of "mirage".
"u" and "ó" are the same sound, similar to English 'oo', but rather short. Sometimes "u" is more like "ł", for example in "auto" or "dinozaur".
"ł" is like the English "w".