Fresh graduates often think that the programming language is the most important thing in a project. However, it is not entirely true because we have many other factors to consider such as structure, database, scalability, availability, testing and many other small things.
The best thing to do is to pick one language that you like the most (the syntax, the ecosystems, the principles etc...) and try your best to master it. However, in practical projects, we dont often use one language (one technology) for everything (one ring to rule them all =)) ), instead we combine multiple technologies (languages) for example, I choose PHP for backend and frontend, and Python or Ruby for database schema migrations and for technologies, I choose Postgresql for primary storage and Redis (or similar db) for caching.
Knowing many programming languages is not bad, the bad thing is to use it wrong. My advice is that dont limit yourself into some particular areas, the more you know the better you will be, that is how developers can "survive". Just make sure that you understand what you are doing
Also, if you know many things, you can compare things, and make better technical decision because we have many candidates to choose