Which server side language should I learn for my purposes?

Ok I realize it's a dumb question, but I don't know where to start.

I use to program since a few years and I realized only these days that I need to know at least one server side language.

In this period I am learning Spring MVC in an internship, but it's freaking me out and I don't like it so I hope not to use it in the future. Perhaps I need a server side language, so here I am.

My question is: what are the differences between the most used server side languages? I mean Java, PHP and NodeJS.

And in what cases are they used? I don't plan to make really big applications, but at the same time I want something significant in my CV.

PS: I know that at the end it's all up to me, but I'd like to hear some advices from people who work in back end development.