Default [Q] i9500 Jumbled internal storage...

Greetings....

This is my first post but i have a quite serious problem, i hope someone here can help...

I just bought my S4 (GT-i9500,16GB) used 2 days ago, it had only 1 month of use, and there wasnīt any hit or scratch marks on the device but i feel something is wrong with the internal storage.

I already know about the 8gb limit thing so thatīs not the case, checking the storage info on the phone settings, i got 3 sections: internal storage, phone storage and sd card, for starters in the phone and internal sections they read 8 and 7 gb free and 16 gb total, the sd card section works normal, as far as i understand there should be only the phone storage section.

and to make things worse, when i connect the phone for usb storage, the internal memory indicates a 1.72gb partition instead of the 8gb or so that the phone is supposed to have, file managers as the ES3 read that same amount of free space.

i believe that my internal storage is damaged, is there a way to fix it or at least have the phone read those 1.72gb correctly on the settings without opening it, spend $100USD+ on repairs, or try to sell it?, i already spent $475USD ($6000 pesos) and i don't want them to go to waste for this.

Any help would be appreciated.

Thanks.