@fsiljelof, We are running H5000 and GNX120 in the boat I sail in. I totally agree that GNX120 documentation is not the best, and that they ship outdated.
In our setup, we use the H5000 as a processor. In the Data Sources in H5 we select the source we want to use (for the anenometer might be obvious, but for GPS you may have more than one antenna).
Then, you can select in the GNX the source for each Data field, you will be able to select the source as well, so make sure you are selecting the source from the H5000.
Notice also that for some data fields in GNX you might be able