You lost me with the second picture
But luckily Google gave clear answer
TOP DEFINITION Nah bruh Something stupid that stupid people say. It comes from 'No, brother', but obviously is much more clever to use 'No' instead of all these stupid combination of stupid slangs.
1: Do you have a crush on anyone?
2: Nah bruh.
1: You *******! You told me you loved me yesterday! How can't you have a crush on me? Stupid. I'm never dating someone who says 'Nah bruh' again!
Classic example of how your girlfriend can get mad if you talk to her stupidly and say 'Nah bruh'