Yes, Citra is only using a single core, however, multi-core won’t change anything. In fact, the 3DS also uses only 1 core for games. A dev tried to do a multi-core test in Citra, but it failed, because the games ran even slower than the latest Nightly at the time.
Your laptop isn’t strong, so don’t expect to get full speed emulation even in the future for a lot requiring games. Low power CPUs in laptops are pretty bad for emulation.