All the cool kids right now are mostly on JavaScript/type script. It’s probably a good place to get started since you’ll need it on the front end.
I’m guessing most work on the U.S. side is react. You can probably pick up a bit of node/react native as you go for the backend and for native dev.
Java is the new COBOL. Big corps luuuuuuuuurve it. It’s not what I would expect a single dev to use. C# is similar but smaller, if you forget unity game dev. And you should forget unity game dev.
Rust is basically a less bad C. If you do things you used to do in C, learn rust. If not, don’t.
Python is also still a thing. If you like it you can probably use it for most things, but if not there are other options.