"I like you, oppa." She saying that she likes an older boy. "Oppa" is used by girls to refer to boys older than them and can also mean brother or boyfriend.
In English, it means "What should I do?" or "What to do?" Used in instances where said party is confused and frustrated with a situation and doesn't know how to handle it.
"What is my name?" She's asking what her name is to confirm he/she knows since a large portion of the song is asking whoever its for to call out to her by her name so she'll recognize them.
