My phone takes 5 hours to charge and drains quickly

Asus Zenfone 5 takes 5 hours to charge and drains quickly. What could be the possible reason. Secondly where can i get it repaired other than the authorised service centre. While charging the phone heats up. I went to Asus center they said they will change the subboard and see if the issue is resolved. If not then i have to change the mother board.