I went on a hiking trip in the Swiss Alps with a Swiss group. I understood them just fine when they spoke German (Hochdeutsch), but they lost me when they started talking Swiss (Schweizerdeutsch). Grandpa Jones sounds like he was making a pretty good approximation of Schweizerdeutsch.

And of course, all my Swiss companions spoke perfect English and French, but they liked it that I could understand German.

-Joe-