I'm Syafira, but you can call me "Fira".

I'm listening to K-pop, – especially Boynextdoor and NCT, P – pop, and R&B, but I didon't know much about R&B.

The ending part is a little unclear. Do you mean it in present tense? Then it makes sense.

I'm Syafira, y. You can call me "Fira"."

Punctuation goes inside the ending quotation mark

I'm a big fan of listening to music and watching movies.

More natural: I love listening to music and watching movies.

I'm currently listening to K-pop, (especially Boynextdoor and NCT), Ppop, and R&B, but I didon't know much about R&B.

I would group the examples of K-pop bands in parentheses like this to look a bit cleaner.

Genres of music are not inherently capitalized (pop, rap, rock). However, the K in "K-pop" is capitalized because it represents "Korean," and nationalities/languages are always capitalized. "R&B" is capitalized because it's an abbreviation. For bands, capitalization of the name is up to the artist. I'm not familiar with this K-pop band, but if they capitalize it as "Boynextdoor," "BoyNextDoor," or "BOYNEXTDOOR," you use the style that they chose.