there is no limit on the number of languages u want to learn, i'll tell u from my past experiences
-In some parts of europe, still few firms are working on Pascal,
-Still fortran is a part of physics education group and is taught to practically every physics student who go for higher studies
-c#, java is favored for web development and some other purposes
-c, cpp still are core languages for device drivers, robotics, compilers, and many other
-HDLs such as verilog, vhdl are for compiler again and also for computer organization
-Depending on your interest, start reading from a side, long way to go