No sentence with "gonna" is natural. Do you by any chance know how much my boss is going to increase my salary? - ok Do you by any chance know how much my boss is going to raise my salary by? - ok . In line with a comment above, "give me" is informal. . You mix "gonna" which is informal in the extreme with the very formal "increase my salary". While the expressions are natural enough, the mix of formal and infomral sounds strange. . raise is both a noun and a verb. I'd go more for How much of a raise is my boss going to give me? (I had to shift "is" as well.) . As aslo stated above, in many places only your boss and you discuss your salary, so the conversation is not exactly natural. :)

can i say :......... how much raise my boss is going to give me?

It feels awkward because why would someone else know you are getting a raise before you do. That being said I would phrase it like this: By any chance, do you know if my boss is going to give me a raise? or By any chance, do you know how much of a raise my boss is going to give me. *Gonna is informal. People will understand you, however people will not take you as seriously.