Here is a WordPress function to get Google reviews by place ID, which you can use as is or modify for your own website needs.

index.php

<?php
/**
 * Get Google reviews by place ID.
 *
 * @param $google_place_id Google place ID.
 *
 * @return void
 */
function kanuka_get_google_reviews( $google_place_id ) {

	// Bail if we don't have a Google place ID.
	if ( empty( $google_place_id ) ) {
		return;
	}

	// Call Google Places API.
	$request = wp_remote_get( add_query_arg( array(
		'place_id' => $google_place_id,
		'key'      => 'YOUR_API_KEY',
	), 'https://maps.googleapis.com/maps/api/place/details/json' ) );

	// The body of the response.
	$body = wp_remote_retrieve_body( $request );

	// Bail if there's a problem.
	if ( empty( $body ) ) {
		return;
	}

	// Decode JSON into PHP array.
	$array = json_decode( $body );

	// Check we have a valid response.
	if ( empty( $array ) || ! isset( $array->result->reviews[0] ) ) {
		return;
	}

	return $array->result->reviews;
}
?>

<?php $reviews = kanuka_get_google_reviews( 'ChIJRWNGE00EdkgRwyaONRrJ4A8' ); ?>
<?php if ( ! empty( $reviews ) ) : ?>
	<ul class="reviews">
		<?php foreach ( $reviews as $review ) : ?>
			<?php
			// Only show 4 or 5 star reviews.
			if ( ! in_array( $review->rating, array( 4, 5 ) ) ) {
				continue;
			}
			?>
			<li class="reviews__item">
				<h1><?php echo $review->author_name; ?></h1>
				<p><?php echo $review->rating; ?> / 5</p>
				<p><?php echo $review->relative_time_description; ?></p>
				<?php echo wpautop( $review->text ); ?>
			</li>
		<?php endforeach; ?>
	</ul>
<?php endif; ?>