I got screwed buying a 2nd hand phone. I need your guys help to fix it

So someone on a facebook group was selling a Galaxy S6 because it wouldnt turn on. He said it worked 1 moment and then suddenly it wouldnt charge or turn on. I figured it was just a software issue and that it might be an easy fix so I bought it for $40. I get home and no sooner than I take it out the back falls right off like the adhesive wasnt holding and the casing over the motherboard easily came off. I look at it closely and realize the battery isnt the original and someone had tampered with it to the point one of the red wires was not connected to anything and it looks like another wire is missing. Here are some pictures and im hoping some tech savy individual can help point me in the right direction on fixing this as I was hoping to surprise my wife with it since her phone is about 5 years old and showing age.

http://ift.tt/2cViD4R
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http://ift.tt/2cVjUsH

I circled 2 points of interest that has me intrigues
http://ift.tt/2d7QJFU


Huge thanks in advance

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