Well! Good news first i have installed latest Manjaro Linux to my old laptop(Asus)
and it works like a dream... so happy. Then i have try install Manjaro to my desktop pc. Well there is this problem: i can install my os but my network seems cut out,so i can not upgrade system.
My motherboard is Gigabyte GA-990FXA-UD5 with uefi bios. I have installed Manjaro with Legacy mode so install works.
I have chosen Manjaro because it is rolling release version.

Any ideas how to solve this issue? Or how to install manjaro at uefi mode?

ps i have installed Solus linux (Gnome) to my desktop and there is no any problems with networking

If you are certain that the network doesn’t work, there are a number of possible causes.

Network interfaces are not recognized. Test this with ip address, which lists all interfaces, their MAC and IP addresses and more info.

If they are not recognized, this might be due to a missing driver. Check the kernel message buffer for errors related to network interfaces.

If they are recognized, do they have IP addresses? If not, the network configuration has a problem. Double-check it.

Does the PC have connectivity to the internet? Try ping 1.1.1.1 -c1. If not, check the physical connection (cable etc.). If yes, check for a name resolution problem: Misconfigured DNS and/or resolv.conf

Why would you install with Legacy mode if your motherboard is UEFI?