1. If they are false, all you can really do is comment. Sadly people can write whatever they want. We had competitors write hundreds of negative reviews over a period of a couple years on reddit/trustpilot other sites. We knew they were competitors because the way they started and concluded the reviews were nearly or completely identical. We were able to get most removed by reporting that's all you can do.
2. You can try reporting fake reviews as non genuine and force them to provide feedback that they are real customers.
Outside of that, you're limited on what you can do.