This is "We speak" generally, is it also like in English when you tell someone you still speak on occasion?
Sure, but not only "on occasion"
Could be in general, from time to time or now. Context would make it more clear
Well Italian does play a bigger role in the opera scene than, say, English...
That reminds me. When I travel to Italy, I want to go an Italian opera theater.
How do you know if it's parli, parliamo, parlate, parlano, parlo, or parla?
Well, it all in the conjugation. For parlare it would be... io parlo I speak (singular) tu parli You speak (singular) lei/lui parla She/he speaks (singular) noi parliamo We speak (plural) voi parlate You all speak (plural) loro parlano They speak (plural)