modify core query

modify-query.php

<?php
add_action('pre_get_posts', function($query) {
    if ($query->is_home() && $query->is_main_query()) {

        $query->set('posts_per_page', 8);

        $currentMarket = get_query_var('market');
        $currentCategory = get_query_var('category');
        $taxQuery = getTaxonomyQuery($currentMarket, $currentCategory);
        if ($taxQuery) {
            $query->set('tax_query', $taxQuery);
        }
    }
});

function getTaxonomyQuery($currentMarket, $currentCategory) {

	if (!$currentMarket && !$currentCategory) {
		return false;
	}

	$taxQuery = array();

	if ($currentMarket && $currentCategory) {
		$taxQuery['relation'] = 'AND';
	}

	if ($currentMarket) {
		array_push($taxQuery, array(
			'taxonomy' => 'market',
			'field' => 'slug',
			'terms' => $currentMarket,
		));
	}

	if ($currentCategory) {
		array_push($taxQuery, array(
			'taxonomy' => 'category',
			'field' => 'slug',
			'terms' => $currentCategory,
		));
	}

	return $taxQuery;
}