Please find the outputs below,

vel@vel-Satellite-C850:~$ sudo apt-get install linux-headers-generic
[sudo] password for vel: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
linux-headers-generic is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 66 not upgraded.
vel@vel-Satellite-C850:~$ lspci -nn | grep 0280
02:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. Device [10ec:8723]
My screen brightness is very high, i am unable to change it using FN keys. Please help.