In the GMB Free connector there are some metrics that are created with calculated fields. These aggregate metrics are not part of GMB Pro but can be easily created with a formula in Data Studio.
Note: Basic formulas often show 'No Data' when working with BigQuery Data Sources, so please use the above formulas as a guide to get past that issue. If you run into any issues please get in contact with support who will be happy to work through your reporting needs.
Calculated Fields in Data Studio
Within Data Studio you can choose to create a calculated field at the Data source level or chart-specific. Wherever possible we recommend to create them at the Data Source level so you can easily reuse the metric across your report without having to maintain multiple formulas. To learn more about the differences and option please see this Google article https://support.google.com/datastudio/answer/6299685
Creating a chart-specific filter
Creating a data source calculated metric