The language of family

If you could wake up tomorrow and be fluent in any language you don’t currently speak, which would it be? Why? What’s the first thing you do with your new linguistic skills? Since the question specifies "language you don't currently speak," I am taking both Spanish and Japanese off the table. I am not, by any means, fluent in either language but I do speak enough that I could get around each country with few problems.

I would like to be fluent in German. My paternal grandfather's family was from Germany and, while I never knew my great-grandfather, it would be nice to know the language he spoke. Sadly, I don't know a lick of German. As for the first thing I would do? I'm not really sure. As far as I know, my immediate family is the end of the family tree. Maybe I could find some distant family in Germany and visit them, but I find that unlikely. I think I would like to learn the language just to have a connection to my ancestors, even if I never use it.

For a similar reason, I'd also like to learn Hawaiian. That is where my maternal grandfather is from. There aren't a lot of non-English speaking members of my family. These two are the closest I get to foreign languages. A great-grandfather I never met and a grandfather who ignored us for most of my life. That is why I don't actually sit down and learn the languages. I'd much rather spend my time working on my Japanese. At least that might be useful to me one day.