If you want to redirect after add to cart product only for selected category for this example category is 'main-category' use this below code to functions.php

add_to_cart_when_match_category.php

function custom_add_to_cart_redirect( $url ) {
    global $woocommerce;

    // Retrieve the product ID from the 'add-to-cart' request parameter.
    $product_id = isset( $_REQUEST['add-to-cart'] ) ? intval( $_REQUEST['add-to-cart'] ) : 0;

    // Check if the product ID is valid and if the category name is 'main-product'.
    if ( $product_id > 0 && has_term( 'main-product', 'product_cat', $product_id ) ) {
        // The URL you want to redirect to for 'main-product'.
        $redirect_url = 'https://yourdomain.com/add_your_url_here';
        return $redirect_url;
    }

    // If the category is not 'main-product', return the original URL.
    return $url;
}
add_filter( 'woocommerce_add_to_cart_redirect', 'custom_add_to_cart_redirect' );