I recommend learning Javascript, if you don't know it. It's very useful, especially for jobs, as there is a lot of work using JS. It's fairly easy to learn too, although there's a lot of frameworks and tools you sometimes need.
It's not a perfect language, but you can pick it up quick and do a lot with it. FreeCodeCamp has a very extensive course which you could have a look at.
Java and C# are ok for some jobs, there is a a lot of work, but it's often the more established corporate type jobs. They are both good languages though. There's more jobs in things like startups using JS. Python is a good language, easy to learn, though there's not a huge amount of work for Python programmers in my area. Lots of work for PHP, JS and C# by me. It does seem to vary by the region though, what is popular.
I'd avoid the niche or domain specific languages unless you want to do a specific project in that area. They aren't very useful for finding jobs or general programming as they lack the libraries and tutorials the major languages have.