Why would anyone give access (API or otherwise) to their funds to an unknown website/service?
I guess you didn't study before posting this.
1. They clearly guide you create trade only API. No withdrawal.
2. The API key stored on your computer using an API client software, once you shut it down, no trading possible on the web platform, they dont store your API on their servers.
3. And more security features in their platform, you can read it up on their site.