How do I fix Garmin GPS update issues?

I am a mountaineer and using Garmin GPS unit for tracking the desired routes easily and comfortably. Often, I am planning various mountaineering trips to some rough and unknown routes, So I believe in using the global positioning system. When I was in the middle of the way, my Garmin GPS unit stopped working. It means that I need to Update Garmin GPS unit in the proper ways. I don’t have the full knowledge to update Garmin GPS unit. I am looking for online help from Garmin experts to update GPS unit. So anyone can recommend the simple ways to update Garmin GPS unit in the proper ways.