Hello and welcome to the forums.
Can we see some more detailed information about your system? Open a terminal window, run the following commands, and post back the results:
1. Your dmesg log file:
...and post back the link that is generated. If you get a message that pastebinit isn't installed, run:
...to install it.
sudo apt-get install pastebinit
2. Info about your video and audio devices:
3. Your active backlight interfaces:
lspci -k | grep -iA2 -e VGA -e Audio
4. What actual functions are the F2, F3, F4, F5 and F6 keys supposed to perform? (i.e. which one is for brightness up, brightness sound, volume up, etc).
for i in /sys/class/backlight/*; do echo $i;cat $i/brightness;cat $i/max_brightness;done