I got about 1 minute into that video and it reminded me that the Garmin training app is not available for Android or, more importantly, for the PC. I learned my GPS 175 (same navigator as the GNC 355) by reading the free hardcopy manual and trying features that were new to me in the aircraft.
Garmin documentation on the GNC 355 is good. Garmin documentation on the G3X Touch system is good. However, in my opinion, the documentation on how the GNC 355 and G3X Touch systems interact is less than adequate. I tried to fill some of the gaps by including information in my AFM supplement as I learned about features and traps.