Life hack: Use a VPN on public Wi-Fis. It's like creating a tunnel that prevents people from stealing data transferred - at least not easily. There are a bunch of free VPNs out there, and no-log VPNs are the best, like Tunnelbear and Hide.me.

Also, don't simply give apps the "Device administrator" tick. Once you give it there's no going back - a malicious app can rape the hell out of your data and your phone. It's like "run as administrator" on Windows so you know what will happen.