The phrase “Samsung Galaxy J5 2016 custom ROM” signals an intersection of elderly-but-popular hardware, community-driven software, and the lifecycle concerns that power users wrestle with. At its core it’s shorthand for: “installing or running a community-built Android firmware on Samsung’s 2016 J5 model,” but that simple definition hides several noteworthy themes.
Go to Wipe > Advanced Wipe.
Select Dalvik / ART Cache, System, Data, and Cache.
Swipe to wipe. (Do not wipe Internal Storage, or you will lose your photos and the ROM zip file).