so... I'm trying to make a simple macropad with a 3x4 matric, a rotary encoder and backlit
but that's not the important part. i have spend many hours on this schematic, and i just want a heads up before ordering the part.
if somebody can see any mistakes (or not) and tell me, i will be very glad.
thank you much 
Your reset circuit looks a bit anemic when compared with say the Arduino Pro Micro which uses the same chip. It may work because the reset pin is, anyway, pulled lightly high. Maybe check it against this: https://www.arduino.cc/en/uploads/Main/arduino-micro-schematic.pdf
Your reset is anemic as indicated by @6v6gt. Below is my standard circuit that works on most processors. You can increase the value of C6 to increase the reset time.
It looks good to me. In my earlier post, I mentioned that D2 on the schematic forces a reset if the voltage drops or if a large negative transient appears on the DC power line. This helps ensure a cleaner reset when faults occur. It isn’t perfect, but it’s certainly better than having no protection at all.
D2 discharges C6 when power is removed but 100pF is very small with a 10kΩ.
100nF (non-polarized) was probably the intended value...
Discharging C6 allows for a reset in case of power glitches.
So would R8
D2 forces the capacitor to discharge with the power source. If it were not there reset could be held high and use only R8 to discharge. You can use almost any diode that you have available, many times the 1N400x is used.
C6 can be either, it is not seeing any high frequencies and one end is grounded.
R9 is the series resistor for the Power On LED, any reasonable value can be used but it needs to keep the current into D1 below its maximum.
The reset pin can be used by a high voltage programmer to do a factory reset so that pin does not have the normal protection diode set. Further, you don't want any higher voltage on that pin (in normal use) than the power rails provide to avoid an unwanted factory reset. Hence the diode.
EDIT
In the original schematic the reset circuit only lacked a pullup resistor, which is optional but recommended. No need for diode or capacitor.
Recommended Reset Circuit for ATmega by Microchip.
1. Internal ESD diode (Reset-pin to Vcc) is removed to prevent HVPP (12V High Voltage Programming Pulse) from being clamped at 5.7V.
2. The external D is the replacement of internal ESD diode, and it is used during normal operation of the MCU. This is to dischage "electrostatic charge" if it happens at the pin.
3. The RC network is the Microchip recommended reset circuit for the MCU. It provides approximately 0.17 ms of reset hold time, allowing the MCU to complete its internal initialization before starting program execution from a flash location pointed by PC.
4. Is it possile that the transient voltage at the Reset pin can rise much above 5V when the RST button is activated? If yes, then the external diode will clamp the transient voltage at around 5.7V, and thereby protecting the intenal Reset circuitry.
Yes I saw that the first time it was posted. I think it is possible to over-engineer stuff. That particular part of the board is probably not really something to concentrate on.
From symbol, C6 appears to be a polar capacitor. Practically, a capacitor of 0.1 nF is of non-polar type.
Isn't there supposed to be a 100nf capacitor at every vcc pin? (post #6)
..im new at pcb design. is all the things about the reset section, like extra does it just make it more stable or is it like necessary and my pcb will explode if i make a mistake?
Yes, they are called decoupling capacitors but they are supposed to be connected between the pin and ground.
I recommend you spend some time learning basic electronics and also read and understand the Atmega32u4 datasheet before you attempt a PCB design.
i have spend many hours
You should be spending days not hours.
This is a good place to learn
https://www.allaboutcircuits.com/textbook/
If you knew what a capacitor was and it purpose you would not have made that mistake
There are other mistakes
Yes!
100 nF = 100 x 10^-9 = 100 x 10^-6 = 0.1 uF.
A gimmick capacitor will work as well. I generally use electrolytic in the one 1uF range because of the nasty electrical systems I am in.
