First of all, thanks a lot for your reply. I tried to follow your instructions, but it doesn't work.
I try to explain what i have done:
I connected the Arduino Nano Every to the pc and I uploaded the sketch ArduinoISP from example; then I connected the pins of the Nano with the Uno ones and finally, as you said, I selected the Arduino Uno board from board and Arduino as Isp from programmer. This is the error I get:
Arduino:1.8.16 (Windows Store 1.8.51.0) (Windows 10), Scheda:"Arduino Uno"
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x03
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x00
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x00
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0xe0
Errore durante la scrittura del bootloader