remove portfolio url

@sunny017 The theme you are using it has inbuilt modified plugin to change slug you can find solution here worked for me.

You just need to change this code

function prefix_change_portfolio_labels( array $args ) {
    $labels = array(
        'name'               => __( 'Projects', 'portfolioposttype' ),
        'singular_name'      => __( 'Project', 'portfolioposttype' ),
        'add_new'            => __( 'Add New Item', 'portfolioposttype' ),
        'add_new_item'       => __( 'Add New Project', 'portfolioposttype' ),
        'edit_item'          => __( 'Edit Project', 'portfolioposttype' ),
        'new_item'           => __( 'Add New Project', 'portfolioposttype' ),
        'view_item'          => __( 'View Item', 'portfolioposttype' ),
        'search_items'       => __( 'Search Projects', 'portfolioposttype' ),
        'not_found'          => __( 'No projects found', 'portfolioposttype' ),
        'not_found_in_trash' => __( 'No projects found in trash', 'portfolioposttype' ),
    );
    $args['labels'] = $labels;

    // Update project single permalink format, and archive slug as well.
    $args['rewrite']     = array( 'slug' => 'project' );
    $args['has_archive'] = 'projects';
    // Don't forget to visit Settings->Permalinks after changing these to flush the rewrite rules.

    return $args;
}