get_terms (or tax_query) for term of current post?

SOLVED

This was what I was looking for and it works like a charm.

function my_query_args($query_args, $grid_name) {

$term_list = get_the_terms( get_the_ID(), 'category' )[0]->slug;

if ($grid_name == 'JTS-SINGLE') {
    $query_args['tax_query'] = array(
        array(
            'taxonomy' => 'category',
            'field'    => 'slug',
            'terms'    => array( $term_list ),
        ),
    );
}
return $query_args;

}
add_filter('tg_wp_query_args', 'my_query_args', 10, 2);