Useless 5ghz connection after firmware upgrade to v1.1.0.84

Hello,

I just have my Netgear router updated to firmware 1.1.0.84 for about 2 days. The 5ghz connection usually drops every few minutes (2.4ghz works just fine), I used speedtest. (net) and it can't check my internet speed due to an unknown problem, then,I tried to do pings but the computer can't ping to all big services like Facebook, Youtube, Apple, Microsoft (Sometimes it can but just for some minutes)

The log was like:

Reply from google.com: time XX ms

Reply from google.com: time XX ms

Reply from google.com: time XX ms

Reply from google.com: time XX ms

Reply from google.com: time XX ms

Request timed out

Request timed out 

Reply from google.com: time XX ms

Reply from google.com: time XX ms 

Request timed out

Desination host unreachable

.........

First,I thought it was my ISP's problem (I even wanted to call them to say what the he** are u doing with my internet lol) but when I use the gateway wifi, and some other routers at my home, it worked perfect, so this should be the Netgear router's problem! (Tried restarting the router multiples time but no work)

Before the firmware update, everything was normal so my prediction is it should be the firmware's prob.

Please help me! Can i get back to my old firmware or how to fix this problem