Hello everyone..thank you all for your help and sorry for late reply.
I want to inform you that the problems that I was having have been solved.
>No SoundI have two sound cards on my laptop:
0 [HDMI ]: HDA-Intel - HDA Intel HDMI HDA Intel HDMI at 0xe3610000 irq 64
1 [PCH ]: HDA-Intel - HDA Intel PCH HDA Intel PCH at 0xe3614000 irq 62
What was happening was that the HDMI was being selected by default.
I then installed pavucontrol and from there I could select the correct device and the problem was solved. 
>No Screen brightness control
This problem was solved by installing the backport kernel 3.16:
apt-get -t wheezy-backports install linux-image-amd64
(Don't forget to add the backport repo to sources.list for e.g: deb
http://ftp.debian.org/debian/ wheezy-backports main non-free contrib
and run
apt-get update)
>No Wifi
This problem was solved as installing the backport wifi firmware:
apt-get -t wheezy-backports install firmware-iwlwifi
Best Regards,
Dwijesh