Javier A Diaz R

I have a Pathfinder that was 5 years warranty and it has 15 now working fine with same battery, but recently started to lose charge so I used to leave it charging for a while under an electric LED or sun light but after several days the warning of LOW charge showed up again, but this and last time the screen become dark brown and no numbers or letters can be read on the seen.
I want to repair it if possible as I love it, please send me instructions where to send it. Thanks, J Diaz