Unhappy [Q] Trying to install custom rom to fake Galaxy S4

Hi all,

Long story short, my brother was scamed to buy Galaxy S4. Now I'm trying to install custom rom on it because the current rom has 50mb of RAM free... I tried with many recoveries, but non was successfull.

Any tips?

Hardware specification of the fake S4 is :

(according to antutu)

Brand : ALPS

Model: GT-I9500
OS: Android 4.4.4
CPU Model MT 6589 (quad @ 1Ghz)
GPU: Mali - 400 MP
Resolution 480x854
RAM: 512 MB
System storage is 120MB (if I can read corectly )

On this current rom GPS is not working (tried somo of Uncle MTK fixes but non worked, I think it's a bad rom)

Any suggestions?

Many, many thx!
I managed to root it with framaroot app.