@LarryM Just to make sure I started the serial monitor, and get the grbl interface.
I knew i had communication with it only the problem was compiling the grbl firmware. I downloaded three different version: 1.1f, 1.0C and grbl-x-carve.
For all i had imported them as a library (as stated in their "manual"). Only after clicking on the compile button i get the following error (also multiple warnings): Sketch uses 32266 bytes (100%) of program storage space. Maximum is 32256 bytes.
Global variables use 1507 bytes (73%) of dynamic memory, leaving 541 bytes for local variables. Maximum is 2048 bytes.
Sketch too big; see http://www.arduino.cc/en/Guide/Troubleshooting#size for tips on reducing it.
Error compiling for board Arduino/Genuino Uno.