command line - Ubuntu login failed

I have Dell Precision T-3620 Workstation and I have installed ubuntu 16.04 in it. It worked well for 1 day. One Day, I had to run a command on the terminal so I pressed Ctrl + Alt + F1 before logging in. I did my work and when I restarted it, I faced a problem. When I write the password, the screen just flashes and the login screen comes again in front of me. When it asks for password, I give it. It waits for sometime and the screen bounces back to the login screen, It recognizes incorrect password and I can login through the terminal but I can't access my files and when I add the correct password, it waits and screen bounces back. Someone said to remove .Xauthority, so I pressed Ctrl + Alt + F1 and typed rm .Xauthority But it still didn't work.

Please anyone help me out.

Thanks in advance..............

Your card is NVIDIA graphic. I have seen many reports of problem. Have a look at this one providing a method to install other drivers: Graphic issues after installing Ubuntu 16.04/16.10 with NVIDIA graphics

Basically, the answer is to wipe out your existing NVIDIA drivers and reinstall them from a specific source.
The center of this answer is :

1. Log into your account in the TTY.


2. Run sudo apt-get purge nvidia-*


3. Run sudo add-apt-repository ppa:graphics-drivers/ppa and then sudo apt-get update.


4. Run sudo apt-get install nvidia-XXX.


5. Reboot and your graphics issue should be fixed.

The next question is what driver version is best for you (nvidia-364 as indicated in that answer, nvidia-340, nvidia-304...)?
To know the existing drivers, refer to the following link: Available NVIDIA drivers
It will then be a matter of trying what best suits your computer. In my case, nvidia-340 works best, in which case instruction 4 would be sudo apt-get install nvidia-340