Below is an example of a configuration, found working with the Fritzbox, based on data fiend provided by the FritzBox. When configuring, modify field values in <> according to your VPN data provided by FritzBox:

Following are connection settings General tab:

Advanced settings configuration (only necessary changes):

Below are proposal settings. FritzBox supports a range of algorithms and options. More details can be found here. Tested configuration is below:
Phase 1:

Phase 2:
