To express in a grammar way,"正在"stands for progressive tense"过"means past tense here. We Chinese seldom use them together. There's another Chinese character standing for progressive tense and always used in the same place with "过", it's "着". The difference between "正在"and"着" is the place we put them in a sentence. We put "正在" right after the subject, while "着" after the verb. Besides, about the word" experience" , we say"体验" or"体味". Often, "体验" is the exact meaning of experience, while "体味" seems to be more elegant or in a literature way. Another tiny point is that when referring to "城市", we always choose to use "座" instead of "个" it doesn't that matter for they are the same meaning, it's just our habit to replace "个"by"座" here. So I think we say" I am experiencing this city now" like this"我正在体验着这座城市"or"我体味着这座城市". Have I expressed clearly? Hope to be of help for you.