Question [Q] Need help please!

I'm sorry for making this thread but i can't seem to find what im troubled for. And im pretty much a NOOB regarding this thing.. so please be understanding.. i have a samsung s4 sgh-i337 running mf3 4.2.2 (rooted) lately charging it took a lot of hours it took me 8 hours just to charge it from 5% to 100% i already closed all the background apps, wifi off, screen off, but still the same, so i think it must be the operating system i don't know if i just done something wrong or what, so I'm thinking to update my phone to the latest version (Kitkat) using samsung kies is it okay? because im rooted right now wouldn't it brick my phone? and does updating my phone correct or replace all the settings that i done wrong or deleted before? which is probably the cause of the slow charging? i really have no idea.. really noob here.. or is there any better way to resolve this? i hope someone can help me, and if there is links regarding answers to my question i would be happy if anyone could post it here.. thanks in advance..