Me wants halp D: (No Xeo allowed (kinda))

[xdot]

So basically the language I am looking for easy to run cross devices, and support good grapgic libraries

C++ - It can be compiled for virtually all platforms out there and there are literally a billion C++ graphics libraries. For instance, SDL (low level cross-platform windowing and input), GLFW, COGL (Object-oriented wrapper around OpenGL), GLM (Linear math library), Ogre (open source game engine) e.t.c. Of course, you could always use the plain low-level OpenGL API (or DirectX - eww).

Btw, I would like to learn all these stuff about Networking (sockets and what not) but I have no idea what they are and in which language they are used. What do you use for your networking-tool or apps?

The actual socket interface and implementation is (usually) written in C. However, most languages provide (thin) wrappers around those functions - e.g. Python's "socket" module. I'd recommend Beej's Guide to Network Programming as it covers almost every aspect of it.