Firstly, I have an exam tomorrow so I can explain everything tomorrow afternoon when I'm back home.
Secondly, the 5.0 update is just horrible. I'd advise against it. I tried it for a few days and I'm back on 4.4.2 now.
Its slow, battery life has worsened and the white background with everything isn't helping. Wait for 5.1 to come, and hopefully that should fix things up.
However, if you still want to flash, be my guest, I'll explain everything tomorrow.
The flashing process takes 5 minutes.
The downloading takes 5 years.
Sent from my SM-G900F