Hello how to redirect user to register page on click to publish ad botton.
Now publish ad redirect user to login page!
Thank you.

@anunturi1.ro
That make sense especially if facebook/google login are enabled, it's best way.
To change this behaviour you will have to swim in code from core, I do not think this is placed in theme item-post.php, maybe ItemActions.php or functions.php, try to search based on error message shown after redirect.