First Time European Travel Tips?

Hi r/travel, I need some tips for a pending trip to Europe.

One of my best friends is moving to Baumholder, Germany in the fall and I'm trying to make plans to visit him and his family when they settle in.

I've been to Puerto Rico where my family's from tons of times and have taken a few road trips here in the States but that's about the extent of my traveling experience. I do love traveling but seeing as I've never taken a trip overseas, I kind of don't know where to begin.

I'm the kind of traveler who doesn't mind doing the tourist-y thing every once and in a while but I usually stick to what the locals enjoy and am open to just about anything.

Any bits of advice would be greatly appreciated from general travel tips, how to get around, how much am I looking at spending while overseas, dealing with the language barrier, recommendations on stuff I absolutely have to do while over there, etc.

Thanks in advance.

EDIT: added some additional detail.