Hello,
I need help. I am using the old osclass script. How can i install osclass 4.4.0 on my classified site that is already in operation without  loosing my data and ads. Pls kindly assist me

@Metalsunny
First make sure to backup everything, just in case.
Then download osclass zip, extract it into your root directory and go to backoffice for upgrade.

I replaced oc-admin, oc-include, index.php and ocload.php with 4.4.0 version and updated it successfully . Thanks anyway. God bless

You should replace everything.

if i replace everything i will loose all my data, lisying and ads images. i just replace the core files i mention above and everything works fine.

I do not think you would lose anything, if you just do replace.