Can you help me updating osclass manually from version 3.6.1 to the latest version because when i am updating with the steps that you posted on the knowledge base then i am getting error on my website :- “ the site can’t be reached “.

You may find steps here:
https://osclass-classifieds.com/installation  (bottom)

In the link that you stated above only tells about the installation procedure but i am asking about the updation from the version 3.6.1 to the latest as the upgrade option is not working in this version of osclass.

That just shows how much you've checked.... 

Osclass upgrade
There are just few simple steps to upgrade your osclass to latest version:
- upload osclass ZIP file into your root directory where osclass is installed
- extract ZIP to replace old files
- go to oc-admin, you will be prompted to perform upgrade
- click on "Upgrade now" button
- once finish, everything is updated and ready to use

Make sure to backup your files and database before each upgrade! In case you got stucked on upgrade, restore your database and file system.

But i have question for step number 2 stated above that if the oc-content folder will be updated then the themes and plugins and uploads all will be replaced which can cause caos in the website so can you tell me which folders can i replace to avoid this problem.

Why would osclass installation contained any themes/plugins except default Sigma theme?

No sir you are getting me wrong i am saying that as step 2 of osclass installation says extract zip to replace old files so as my website contains old files of osclass version 3.6.1 so my website contains all themes and plugins so if will replace the files all themes and plugins would be lost.
Thats why i am asking to specify the folders of osclass installation to be replaced.

Never seen unzip that would be removing files not present in archive 

ok i will check on my localhost and get back to you in this matter ASAP   

Thank you I have updated osclass successfully with your steps.

Thank you I have updated osclass successfully with your steps.

Awesome, hope that process was simple