www.chinaphonearena.com

I am going to buy this phone and I have a few questions:
I came from i9300 galaxy samsung and now I am going to buy this phone because of its price

my questions:
1.I found by searching ont his forum and others that it has wifi connection problem meaning after a couple of minutes it disconnected..is there a fix to it ?
2. how do i upgrade firmware?
3. are there any custom roms ?
4.gps fix ? is it reliable?

OS: Android 4.2.1
CPU: MTK6589T Quad Core 1.5GHZ
GPU: PowerVR SGX 544MP
RAM 1GB,DDR3
Storage 16GB
Sim Card: Dual SIM Card Dual Standby
Brand:
2G: GSM 850/900/1800/1900MHz
3G: WCDMA 850/2100MHz
Service Provide: Unlocked
MS mode: WCDMA/GSM
Shell Material Plastic
Screen: Capacitive Touchscreen, 1920*1080 High-resolution Screen
Size: 5 inch
Resolution: 1920*1080 IPS
Screen PPI: 440
Gravity Sensor: Yes
Visible Angle: 178°
Display: Retina IPS
Navigation GPS+AGPS Navigator
Daul Camera: Front Camera 2.0M ,8.0M Pixels High definition back camera Auto Forcus
Wireless transmission 3G, WIFI 802.11b/g/n, Bluetooth 4.0, EDGE, HSDPA, HSUPA
HSUPA Support 5.76 Mbps
HSDPA Support 7.2 Mbps/42Mbps