Translation by @presumenothing:
Sera “How about your boyfriend Shinichi-kun?”
Ran “Eh?”
Sera “He knows how to play guitar too right?”
Ran “S-Shinichi does know how to play the violin…” “But… guitar?” “His singing ability is same as Conan’s…” “Isn’t it…”
Conan (thinking) *Really sorry that I’m tone deaf…*
Okay, but why does Sera seem convinced that Shinichi can play guitar?