Last night I did a very stupid thing by changing the owner of the directory /usr using the following commands
su password: chown username:username /usr
Now the problem is that I cannot access the network card (i.e. I cannot access the wifi), sound card(i.e. I cannot control the sound and also the sound card is not shown in the sound settings) and also I cannot use the sudo command to gain the super user privileges. Need help as soon as possible. Thank you in advance.