Language Barrier

[Milit]

I have had the intention of doing some travelling when financially feasible, and I am looking to do some solo trips from maybe next year or the year after.

I have never travelled abroad before, and I am looking for some advice from those that have. The prospect of travelling solo doesn’t bother me as I am quite quiet/private.
An issue that I wanted advice on was the language barrier. I’m not arrogant enough to think that every country should speak English, however I don’t speak any other languages myself.

I am wondering how common it is to encounter English speakers once you start to get off the beaten track: when travelling between places that perhaps wouldn’t be obvious tourist places, or refuelling for example

If there was one language that people would recommend to learn some of for travel mostly in continental Europe what would it be? Or perhaps it’s possible to get by with just some common phrases?

The truth is I’m simply not a very outgoing person, bit of an introvert. But I am also a realist and I am aware it isn’t possible to travel without encountering at least some people.

Thanks folks.