The expression "going bananas" means "to go crazy," though they are just a little different in the level of crazy haha. An example would be: "When he saw a cat in his shower, he went bananas!"

me estoy volviendo loco. Similar expression are : I'm going nuts . I'm cracking up. Losing my mind. I'm freaking out.

"What does the expression 'I am going bananas' mean?" - this is the correct sentence. We never use "what does mean...", as the phrase is completely wrong.