Who do you say good morning dude in Japanese?

Answer 1

As this exact phrase would be strange/unnatural if translated directly, a more appropriate translation would be a slightly vulgar/very informal and colloquial version of "good morning" used expressly among close friends. This is 'ossu.'

Answer 2

In Japanese to say "Hello" you can konnichiwa, or koncha and if you want to say "heyy!" you can say nee! I don't think theres equivalent Japanese for our Hi dude in English so just stick to that.