Basically we don't know the risk in every site if you invest money in a site first is you don't know if the site was trusted there are site that can give you small profit but many site are just scamming people who invested.
Investment was risky because you doesnt have assurance that it will be successful or not. There are sites that always scammed your bitcoin so must be careful. Before you invest your bitcoin. make sure first that the site is trusted and doesnt have any negative experienced. Scammers are anywhere now so be careful.