どう思いますか？ What do you think? についてどう思いますか？ What do you think about/of? このまちについてどう思いますか？ What do you think about this city? どうでしたか？ How was it? Note that the interrogatives in English are different. You can just remember them as something like idioms. I often hear from English speakers that なんと/なんて思いますか in Japanese. This is wrong. Similarly, from Japanese speakers when they try to speak English; How do you think (because どう in Japanese is in most cases translated into how). I am not sure why we say "どう" and why it is "what" in English. There are some explanation sites written in Japanese but I can't explain by myself. https://eikaiwa.weblio.jp/column/phrases/handy_english_phrases/what-do-you-think

I recommend to just memorize "What do you think?" is translated "どう思いますか。" in Japanese. It sometimes happens. Another example like that is this. "have been to" literally means "いたことがあります", but it is translated "行ったことがあります". It is because Japanese neither say "何と思いますか" nor "いたことがあります". Adding to it, I remmeber "what kind of" is usually translated "どんな". What kind of food is that? それはどんな食べ物ですか。

この means "this." まち means "town" or "city." について means "about." どう is a "manner adverb" meaning "what way" or "which way" (according to a grammar book that I have). 思います is a polite way of saying 思う meaning "to think." か is a particle that makes a sentence into a question. このまちについてどう思いますか？ means "What do you think about this town [city]?" どう (what way) in どう思いますか works as an adverb and is modifying the verb 思います (think). All of my Japanese dictionaries say that どう is an adverb. I would say it can have different meanings according to how it's used and can be translated differently in English. For example, どう could be translated as "what," as in "What do you think? (どう思いますか？)," "how," as in "How was it? (どうでしたか？)," or "why? (どうしてですか？)." This isn't exhaustive, but I hope this helps even a bit.