C++

Get into web dev, lots of applications there. Start off with basic HTML, CSS and Javascript. Then move on to learning jQuery, Node.js and Angular.

If web dev isn't your thing, consider learning Python or Go.

Don't worry if it seems daunting at first, it's not that hard to get a hang of it.

First learn how to make static websites with just HTML, CSS and Bootstrap. This forms the skeleton of your website.
After you've mastered that, learn Javascript and the jQuery library. This gives your web page life and functionality.
Take some time to get comfortable with the first two, then consider learning a framework like Angular, Vue or React - this allows you code a web application with the same mindset as if you were coding something in say Java or C++

Also, if you have time, read Data Structures and Algorithms in Java. This is the bread and butter of Computer Science.

Trust me, it's worth it in the end. The stuff they teach in school barely scratches the surface. It's better to start learning now, otherwise when you go to college you'll realize that there are loads of people just like you who know more than you.

Hello dark68360,
if you are planning a scientific/engineering career (there was some info about interests in science in your profile previously), it can be of great help to know C/C++, Microsoft Visual Basic and maybe Fortran (or a more progressive F language). For certain applications, microcontroller/DSP programming skills can also be useful. People who can write programs are nowadays at a very high demand in scientific institutions.

However, you should first find a task/problem that you want to solve by writing a program - otherwise it can be difficult to keep learning. Many people take up programming only at university where they can use it to solve a scientific task.

P.S. Also, many programming courses begin with low-level coding. At my university we first learned about machine code & algorithms, wrote programs for Turing and Markov machines and studied x86 assembly language, and only later moved to C++ as an example of a high-level language. Starting with the basics allows to understand how exactly a computer works and how to make your programs run faster.

Hope this helps!

Well, I had a couple of programming courses during my own (ongoing, hopefully) University studying, and by most part it was for scientific applications. We used C to work with raw data (which we then could export to GNUPlot, or Excel, or Origin), then with C++ to create programs with interface so we could visualize said data (e.g. we had a program that could draw electric field intensity from a number of randomly placed positive or negative charges), then C again for working with COM-ports (mostly recording raw data from them and then dumping it into Excel), C++ again for network, a bit of HTML/JavaScript for basic web designing and some Assembler for microcontrollers. One of my groupmates is working on a graduation paper about creating a program for a spectrophotometer at Geochemistry Institute, but unfortunately, I didn't manage to learn more since I've got my own GP to work on.

I more or less learned the ropes about these languages, but tend to forget such stuff just as fast. I think it's been an year since I last did any coding and I think I have completely forgotten anything I've done.

Well, if I won't mention making custom triggers for some Warcraft III custom maps, though what I do there has little to do with actual coding.

P.S. You might or might not find one book useful, Brian Kernighan & Dennis Ritchie, The C Programming Language. It's the book our teacher recommended for learning the ropes.

always keep in mind.... I never learned any of the above

Thats just many years of doing many mistakes and learning from them.