When users add their listings, the listings get the inactive status, but they are still added to site, they are viewable from anyone on site and everyone that see the spefic ad, see also the message that this post waits validations from admin (like if it was their listing).

When i approve the listing from admin, then the flash message disappears, and the listing keeps being available to anyone for view

Have you disabled item validations for users?
Have you tried to reinstall plugin?

yes i have disabled user validation for users. So i should uninstall and reinstall the plugin?

@KaloSex
That is not needed. If plugin use b_active field of listing, then item cannot be visible once published (until there is something different that force b_active field to be 1 instead of 0.)
You can validate it in database on t_item table.

yes but as i told, it is visible to everyone. Also, everyone sees the flash message that the item needs validation. So here is what info i can give you:
On the backend on the listing page, the listing shows as Active
On the Item validation plugin, it shows Inactive and that it needs validation.

I upload two screenshots. One of the sql and one of the listing that anyone can see the flash message

The ad disappears only if i go to oc-admin/index.php?page=items and i click to deactivate it from there.

So the problem is that once posted, it shows as activated on the backend listings list

oc_t_item.b_active must be 0.