Dear Simone,

I suggest you to use Assemply programming as it's easy to learn make you familiar with the hardware you are using (registers ,timers ....etc.)

If you have a previous idea of 8086/8088 microprocessor programming we will find it more easier to program 8051 family of microcontrollers as the instructions are approximately similar.

So i think you have to start with assemply programming as a beginner then once you became expert with it you can try C progremming.

Regards
Hatem Zakaria