can i cpu upgrade in notebook asus x556uq?

Laptops are very hard to upgrade something other then memory or storage. First, I don't think they make 7th gen "u" CPUs that have quad cores. If you drop in a non "u" 7th gen quad core chip (such as 7700hq), if the CPU is not soldered and it works at all, it would destroy your battery life. The "u" chips are for low powered devices. So your battery was not designed to handle a higher powered CPU.