I solved some of the problems and I am getting closer to find a proper solution for the remaining ones:


2: Why LCD screen is off and how do I put it on?
-> because it was not plug the right way (no indication about the right way) FIXED

4: Why the firmware installation is freezing and how to properly install my "P802NV20.hex" one?
-> apparently, the avrdude conf is not right, same problem as the 6.4 NOT FIXED

6.4: Why have I the "avrdude stk500_getsync() not in sync" error and how do I reach the board?
-> see point 4 NOT FIXED

7: Why is it possible to reach the printer using repetier host/server and impossible with cmd/arduino IDE?
-> not a clue... I have to understand about the differences regarding the communication protocoles between avrdude and repetier host/server NOT FIXED

9.1: How can I set a Z-offset?
-> that's not a proper problem, I have a sensor for the auto-levelling bed feature, I have to use it FIXED

9.4: I think the problem is because the temperature of the bed warm the first layers and not the other one and/or the printing speed is too high, is that right?
-> all wrong, the speed of the printing was too high. So I properly sliced and everything is perfect! FIXED