Remove current portfolio item from portfolio grid

Hi,
On a single portfolio item I have a portfolio grid but I want to remove the current portfolio item from that grid.
I searched the forum and already tried different suggestions, e.g.

function ava_exclude_portfolio($query) {
     $query->set( 'offset', '1' );
}

add_action('pre_get_posts', 'ava_exclude_portfolio');

But unfortunately it didn’t work.

Also I want a pagination for the grid which paginates after every 4 items. How can that be done?