Phone guardian is a free mobile VPN. In general, I would never recommend using a free VPN — there are way too many privacy concerns.
That said, if you only need a fast and free VPN to do something unimportant (and not enter any sensitive data like credit card numbers or passwords), then Phone Guardian is as good as any other free VPN. But I would never recommend you use this or any other free VPN regularly, especially not to connect to an online account or access any kind of sensitive information.
If you need full-suite internet security protections, read about the best antivirus programs with a VPN.