standalone arduino help

I am trying to make arduino on pcb for a permanent project
This is my first time drawing a pcb layout and I wonder if anybody can help me checking it
thanks

You appear to have Aref connected to AVCC. Don't do that, it connects to 5V internally via a software controlled mux.
You need 0.1uF caps from VCC, AVCC, Aref pins to Gnd. Mount them close to the pins.
Are you going to bring the IO signals out to connectors so the chip can interact with the world? Add some connections for +5 & Gnd also.

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CrossRoads:
You appear to have Aref connected to AVCC. Don't do that, it connects to 5V internally via a software controlled mux.
You need 0.1uF caps from VCC, AVCC, Aref pins to Gnd. Mount them close to the pins.
Are you going to bring the IO signals out to connectors so the chip can interact with the world? Add some connections for +5 & Gnd also.

thanks a lot but can you please explain it a little bit...this is my first ever circuit...and I am a medical doctor!

Look at the Promini schematic for an example of a minimal circuit. (This is a 32-pin surface mount chip, different pin numbers than the 28-pin DIP you are using. The IO functions are the same tho).
Notice how AREF pin just has capacitor C1 to Gnd.
Also notice caps C10 and C3, from VCC to Gnd. These are decoupling caps, they provide little surges of current to the VCC and AVCC pins to provide power for fast internal switching of transistors in the chip.
Notice JP6 and JP7, these allow to connect the IO pins to other parts, like LEDs, buttons, servos, sensors, etc.
JP1 lets you conveniently plug on a FTDI Basic for serial downloads and to connect to a PC, then you can interact with your card via the serial monitor, useful for debugging your code. It also helps to have a 0.1uF cap C2 between the DTR pin and the Reset pin of the uC so the PC software can reset the chip to start a download.
Not shown is an ICSP header:
MISO 1 2 +5V
SCK 3 4 MOSI
Reset 5 6 GND

This lets you conveniently connect a Programmer to either install a bootloader, or to install code without a bootloader without going thru the Serial port.