How to disable or hide title field when posting new ad? I dont need this field at all.

It's required field by Osclass, theme & plugins, cannot be disabled.
What you could try is to hide it via CSS and generate (populate input) title based on user input (ie category + location).

You can change it so that it is not displayed in item.php after posting.


<?php echo osc_item_title(); ?>

It's required field by Osclass, theme & plugins, cannot be disabled.
What you could try is to hide it via CSS and generate (populate input) title based on user input (ie category + location).

how to generate this input? Can you give me a code?

I do not have it, require little bit of testing.
If you have no skills, do not do it and look for developer.

Something basic would be:
$(document).ready(function() {
  $('input[name="title[en_US]"]').val('Dummy title');
});

And hide title (this is for Epsilon):
.row.ttle {display:none;}