After installing an update , loose my Desktop directory.

Thank you for taking the time to report this issue and helping to make Ubuntu better. Examining the information you have given us, this does not appear to be a bug report so we are closing it and converting it to a question in the support tracker. We understand the difficulties you are facing, but it is better to raise problems you are having in the support tracker at https://answers.launchpad.net/ubuntu if you are uncertain if they are bugs. You can also find help posting your problem in the support forum of your local Ubuntu's community http://loco.ubuntu.com/ or asking at http://askubuntu.com. For help on reporting bugs, see https://help.ubuntu.com/community/ReportingBugs.

If you log on as guest is it OK there?

Ubuntu 18.04 does not allow guest login right ?
Do you want me to switch to lightdm then try ?

Yes it does allow guest. Log off then log in as guest

I have tried it , i don't see an option for guest log in. I can only see existing user option for log in.

I have tried it , i don't see an option for guest log in. I can only see existing user option for log in.

If you log in with your normal user and open a terminal window, what output do you receive for the commands

whoami
uname -a
lsb_release -crid
ls -l /home
ls -l /home/`whoami`

It prints the output as fololws:
divyank@divyank-B250M-D3H:~/test$ whoami
divyank
divyank@divyank-B250M-D3H:~/test$ uname -a
Linux divyank-B250M-D3H 4.15.0-51-generic #55-Ubuntu SMP Wed May 15 14:27:21 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
divyank@divyank-B250M-D3H:~/test$ lsb_release -crid
Distributor ID: Ubuntu
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Codename: bionic
divyank@divyank-B250M-D3H:~/test$ ls -l /home
total 4
drwxr-xr-x 23 divyank divyank 4096 Jun 10 18:00 divyank
divyank@divyank-B250M-D3H:~/test$ ls -l /home/`whoami`
total 64
drwxrwxr-x 4 divyank divyank 4096 Jun 10 18:00 data
drwxr-xr-x 3 divyank divyank 4096 Feb 6 13:00 Documents
drwxr-xr-x 2 divyank divyank 4096 Jun 1 13:23 Downloads
-rw-r--r-- 1 divyank divyank 8980 Oct 3 2018 examples.desktop
-rw-r--r-- 1 divyank divyank 11037 Jun 8 16:16 hash_table.c
drwxr-xr-x 2 divyank divyank 4096 Oct 3 2018 Music
drwxr-xr-x 2 divyank divyank 4096 Jun 8 18:15 Pictures
drwxr-xr-x 2 divyank divyank 4096 Oct 3 2018 Public
drwxr-xr-x 7 divyank divyank 4096 Apr 26 09:52 snap
drwxr-xr-x 2 divyank divyank 4096 Oct 3 2018 Templates
drwxr-xr-x 2 divyank divyank 4096 Jun 10 17:58 test
drwxr-xr-x 2 divyank divyank 4096 Oct 3 2018 Videos
divyank@divyank-B250M-D3H:~/test$

The home directory is there and there are some subdirectories shown below your home directory.
Are they all empty?

Only "Videos" directory is empty.

So are your files there (except those in the Videos subdirectory)?

Yes those are there, but files and folders which i had in my desktop directory those are not there, Desktop directory is missing.

Yes i found it there , Thank you for the response, and i am sorry it was my mistake.

Thanks Manfred Hampl, that solved my question.