> Will RX 560 4GB fit in my computer?
Presumably, you can measure the length of the current graphics adapter, and you can see whether it occupies the space for one slot, or if it is "double-wide" -- physically taking the space for two cards.
I hope that you can Google-search for the specifications of the "RX 560 4GB", to determine its length, and whether it is "double-wide", and whether you have enough physical space available for a "double-wide" card to fit in the available space.