Okay, guys after several days of pain (and nearly switched back to win7), I found a solution for the 2 most common wifi problems (I had both).
First, the "limited connectivity" problem:
Open a command prompt (Search/type "cmd"/press Enter)
Type these (they are changing the global tcp settings, press ENTER after every line of command):
IPCONFIG /FLUSHDNS
NETSH INT TCP SET HEURISTICS DISABLED
NETSH INT TCP SET GLOBAL AUTOTUNINGLEVEL=DISABLED
NETSH INT TCP SET GLOBAL RSS=ENABLED
NETSH WINSOCK RESET
Then restart your wifi adapter or restart your computer (you can find other sources about these commands anyway)
This one solve the "limited connections" problem.
Second, the frequent disconnects or dropping from wifi network:
As I noticed, it is a driver related problem.
Change your current "manufacturer" wifi driver to a "Windows" driver for your wifi adapter (you can choose from a list when you'd like to change the driver of your wifi adapter in the Device Manager).
Since this change, my wifi have not dropped from the wifi network.